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[[File:SI base units.svg|thumb|right|275px|
Li sett SI unités basic
{|
|- 
! Simbol !! Nómine !! Quantitá basic
|-
| style="text-align: centre;" | s   || [[seconde]] || [[témpor]]
|-
| style="text-align: centre;" | m   || [[metre]] || [[longore]]
|-
| style="text-align: centre;" | kg  || [[kilogramme]] || [[masse]]
|-
| style="text-align: centre;" | A   || [[ampere]] || [[electric currente]]
|-
| style="text-align: centre;" | K   || [[kelvin]] || [[temperatura termodinamic]]
|-
| style="text-align: centre;" | mol || [[mole (unité)|mole]] || [[quantitá de substantie]]
|-
| style="text-align: centre;" | cd  || [[candela]] || [[luminosi intensitá]]
|-
|}
]]

Li '''Sistema International de Unités''', con li international abreviation de '''SI''', es li modern forme del [[sistema metric]] e li max usat [[sistema de mesuration]] in li munde. 
<ref name="SIBrochure9thEd">{{citation |title=The International System of Units (SI) |author=International Bureau of Weights and Measures |author-link=New SI |date=20 May 2019  |edition=9th |isbn=978-92-822-2272-0 |url=https://www.bipm.org/utils/common/pdf/si-brochure/SI-Brochure-9.pdf| archive-url = https://web.archive.org/web/20211018184555/https://www.bipm.org/documents/20126/41483022/SI-Brochure-9.pdf/fcf090b2-04e6-88cc-1149-c3e029ad8232 |archive-date=18 October 2021 |url-status=live}}</ref> Etablisset e mantenet per li [[Conferentie General de Pesas e Mesuras]] (CGPM), it es li sol sistema de mesuration con un oficial statu in presc omni pais in li munde, usat in scientie, tecnica, industrie, e quotidian comercie.

Li SI contene un [[Coherentie (unités de mesuration)|coherent]] sistema de [[unités de mesuration]], con sett [[Unités basic del SI|unités basic]]. Tis es li [[seconde]] (simbol s, li unité de [[témpor]]), [[metre]] (m, [[longore]]), [[kilogramme]] (kg, [[masse]]), [[ampere]] (A, [[electric currente]]), [[kelvin]] (K, [[temperatura]] termodinamic), [[Mole (unité)|mole]] (mol, [[quantitá de substantie]]), e [[candela]], (cd, [[luminosi intensitá]]).

Li sistema posse acommodar coherent unités por un ínlimitat númere de additional quantitás. Tis es li coherent [[Unités derivat del SI|unités derivat]], quel sempre posse esser representat quam productes de exponentiationes del unités basic. Por exemple, li SI unité de [[velocitá]] es metre per seconde, m⋅s<sup>−1</sup>; de [[acceleration]] es metre per seconde quadrat, m⋅s<sup>−2</sup>; etc. Tis anc posse esser scrit quam m/s e m/s<sup>2</sup>, proprimen. Duanti-du coherent unités derivat have special nómines e simboles. Por example, li [[Newton (unité)|newton]] (N) es li unité de [[fortie]], equivalent de kg⋅m⋅s<sup>−2</sup>. Li sett unités basic e li 22 coherent unités derivat con special nómines e simboles mey esser usat in combination de expresser altri coherent unités derivat. Por exemple, li recomandat unité del [[Campe electric|fortie del campe electric]] es li volt per metre, V/m, u li [[volt]] es li derivat unité de [[Voltage|differentie de potentiale electric]]. Li volt per metre es equivalent de kg⋅m⋅s<sup>−3</sup>⋅A<sup>−1</sup> in li basic unités.
 
Pro que li dimensiones de coherent unités es comod por alcun usus e ne por altres, li SI furni 24 [[Metric prefixe|prefixe]]s que, quande addit al nómine o simbol de un coherent unité da 24 additional (íncoherent) unités con un separat nómine e simbol. Ti íncoherent unités es sempre decimal multiplicas e submultiplicas del unités coherent. Por exemple, li SI coherent unité de longore es li metre, ma por distanties geografic e stradal, on presc sempre usa [[kilometre]]s. Un kilometre es 1000 metres, e li prefixe metric '[[kilo-]]' (simbol 'k') representa un factor de 1000. Li SI es intenter esser un sistema evoluent. Li unités e prefixes es creat e li definitiones del unités es modificat per international acorde quam li tecnologie e precision de [[mesuration]] avansa.

Desde 2019, li grandores de omni SI unités ha esset definit per declarar que sett ''definent constantes'' have exact numeric valores quande expresset in terminos de lor SI unités. Li definent constantes es li [[rapiditá de lúmine]] in un [[vacuo]] ''c'', li [[standarde de cesium|hipertenui transitional frequentie de cesium]] Δ''ν''<sub>Cs</sub>, li [[constante de Planck]] ''h'', li [[charge elementari]] ''e'', li [[constante de Boltzmann]] ''k'', li [[constante de Avogadro]] ''N''<sub>A</sub>, e li [[luminosi eficacie]] ''K''<sub>cd</sub>. Li natura del definent constantes extende de fundamental constantes de natura quam ''c'' al purmen tecnic constante ''K''<sub>cd</sub>. Li present metode de definir li SI es un resultate de un continuat movement vers un crescentmen abstract e idealisat formulation, in quel li [[Realisation (metrologie)|realisations]] del unités es separat conceptualmen del definitiones e ne have fisic prototipes. Li ultim prototip usat per li SI esset un cilindre del platin-iridium que definit li kilogramme. 
 
Li original motivation por li developation del SI esset li diversitá de unités que hat crescet intra li [[centimetre–gramme–seconde sistema de unités|centimetre–gramme–seconde]] (CGS) sistemas (specificmen li inconsistentie inter li sistemas de [[electrostatic unités]] e [[electromagnetic unités]]) e li manca de coordination inter li varie areas de studie que usat les. Li CGPM, quel esset fundat per li [[Convention del Metre]] de 1875, associat multi international organisationes de etablisser li definitiones e standardes de un nov sistema e de standardisar li regules por scrir e presentar mesurationes. Li sistema esset publicat in 1960 quam un resultate de un initiative que comensat in 1948, qualmen it es basat sur li [[MKS sistema de unités|metre–kilogramme–seconde sistema de unités]] (MKS) in vice de alcun variante del CGS.

==Unités basic e derivat==
Li Sistema International de Unités consiste de un gruppe de [[SI unités basic|unités basic]], [[SI unités derivat|unités derivat]], e un gruppe de decimal-basat multiplicatores que es usat como [[SI prefixe|prefixes]].<ref name="SIBrochure">SI Brochure, pages=103–106</ref> Li unités, excludent prefixat unités, forma un [[coherent sistema de unités]], quel es basat sur un sistema de quantitás talmen que li equationes inter li numeric valores expresset in coherent unités have exactmen li sam forme, includent numeric factores, quam li corespondent equationes inter li quantitás. Por exemple, 1&nbsp;N = 1&nbsp;kg × 1&nbsp;m/s<sup>2</sup> di que ''un'' newton es li [[fortie]] necessi a [[Acceleration|accelera]] un masse de ''un'' kilogramme a ''un'' [[metre per seconde quadrat]], quam afin per li principle de coherentie al equation relater li corespondent quantitás: ''F'' = ''m'' × ''a''.

Li unités derivat aplica a quantitás derivat, quel mey esser expresset per definition in términos del quantitás basic, e talmen ne es independent;  
por exemple, [[electric conductantie]] es li inverse de [[electric resistantie]], con li consequentie que li siemens es li inverse del ohm, e similmen, li ohm e siemens posse esser substituet con un proportion de un ampere e un volt, pro que ti quantitás have un definit afinitá a unaltru. Altri util derivat quantitás posse esser specificat in términos del quantitás basic e anc unités derivat que ne have un nómine in SI, quam acceleration, quel es definit in SI unités quam m/s<sup>2</sup>.

===Unités basic===

Li SI unités basic es li elementari partes del sistema e omni altri unités es derivat de les.

{| class="wikitable" style="margin:1em auto 1em auto"
|+ <big>SI unités basic</big><ref name="NIST330">NIST 330, p. 6</ref><ref name="BIPM1975">
[http://old.iupac.org/publications/books/author/mills.html Quantities Units and Symbols in Physical Chemistry], IUPAC</ref><ref name="archive1975">{{cite book
|url=https://archive.org/details/internationalbur420page |pages=[https://archive.org/details/internationalbur420page/page/238 238]–244 |title=The International Bureau of Weights and Measures 1875–1975: NBS Special Publication 420 |date=20 May 1975 |editor-last1=Page |editor-first1=Chester H. |editor-last2=Vigoureux |editor-first2=Paul |publisher=[[National Bureau of Standards]] |location=[[Washington, D.C.]]}}</ref>
|-
! scope="col" | Nómine de unité
! scope="col" | Simbol
! scope="col" | [[Dimensional analise|Dimensional simbol]]
! scope="col" | [[Fisic quantitá|Nómine de quantitá]]
! scope="col" width=80 |Tipic simboles
! scope="col" | Definition 
|-
! scope="row" | [[seconde]]<br/><ref group="n">
Intra li contextu del SI, li seconde es li coherent basic unité de témpor, e es usat in li definitiones de unités derivat. Li nómine "seconde" historicmen provenit quam esser li duesim-nivellic [[sexagesimal]] division (1/3600) de alcun quantitá, li [[hor]] in ti casu, quel li SI classifica quam un "acceptat" unité junt con su prim-nivellic sexagesimal division del [[minute]].</ref>
|style="text-align:center" |s
|style="text-align:center" |T
| [[témpor]]
|<math>t</math>
|Li duration de 9.192.631.770 periodes del radiation corespondent al transition inter li du [[Hiperfin structura|hiperfin]] nivelles del [[statu fundamental]] del [[cesium-133]] atom.
|-
! scope="row" | [[metre]]
|style="text-align:center" |m
|style="text-align:center" |L
|[[longore]]
|<math>l</math>, <math>h</math>, <math>a</math>, <math>b</math>, <math>x</math>, <math>y</math>, <math>r</math>, etc.<ref>Simboles de longore varia grandmen con contextu.</ref>
|Li distantie propagat per lumine in vacuo in 1/299.792.458 secondes.
|-
! scope="row" | [[kilogramme]]<br /><ref group="n">Malgré li prefixe "kilo-", li kilogramme es li coherent basic unité of masse, e it es usat in li definitiones del unité derivat.</ref>
|style="text-align:center" |kg
|style="text-align:center" |M
|[[masse]]
|<math>m</math>
|Li kilogramme es definat per usar li [[constante de Planck]] ''h'' quam exactmen 6,62607015 x 10<sup>-34</sup> J.s (J = kg⋅m<sup>2</sup>⋅s<sup>−2</sup>), donat li definitiones del metre e li seconde.<ref name="NIST 2018-11">NIST 2018-11</ref>
|-
! scope="row" | [[ampere]]
|style="text-align:center" |A
|style="text-align:center" |I
|[[electric currente]]
|<math>I,\; i</math>
|Li currente de exactmen 1 / 1,602176634 x 10<sup>-19</sup> vez li [[charge elementari]] ''e'' per seconde. To es circa 6,2415090744 x 10<sup>18</sup> elementari charges per seconde.
|-
! scope="row" | [[kelvin]]
|style="text-align:center" |K
|style="text-align:center" |Θ
|[[temperatura|temperatura<br />termodinamic]]
|<math>T</math>
|Li kelvin es definat per assignar li fixat valore numeric del [[constante de Boltzmann]] ''k'' a 1,380649 x 10<sup>-23</sup> J/K, (J = kg⋅m<sup>2</sup>⋅s<sup>−2</sup>), donat li definition del kilogramme, li metre, e li seconde.
|-
! scope="row" | [[Mole (unit)|mole]]
|style="text-align:center" |mol
|style="text-align:center" |N
|[[quantitá de substantie]]
|<math>n</math>
|Li quantitá de substantie de exactmen 6,02214076 x 10<sup>23</sup> elementari entitás.<ref group="n">Quande li mole es usat, li elementari entitás deve esser specificat e mey esser [[atom]]es, [[molecul]]es, [[ion]]es, [[electron]]es, altri particules, o specificat gruppes de tal particules.</ref> Ti quantitá es li fixat valore numeric del [[constante de Avogadro]], math|''N''<sub>A</sub>, quande expresset in the unite mol<sup>−1</sup>.
|-
! scope="row" | [[candela]]
|style="text-align:center" |cd
|style="text-align:center" |J
|[[intensitá luminosi]]
|<math>I_v</math>
|Li intensitá luminosi, in a alcun direction, de a fonte que emisse radiation monocromatic del frequentie 5,4 x 10<sup>14</sup> hertz e con un radiant intensitá in ti direction de 1/683 watt per [[steradian]].
|-
| colspan="6" |
;Notes
{{reflist|group="n"}}
|}

===Unités derivat===

Li unités derivat del SI es format per potenties, productes, o quotientes del unités basic, e ili es potentialmen ínlimitat in númere.<ref name="SIBrochure"/><ref name="NIST330"/>Li unités derivat es associat con li derivat quantitás; por exemple, [[velocitá]] es un quantitá que es derivat del basic quantitás de témpor e longore, e talmen li unité derivat in SI es metre per seconde (simbol m/s). Li dimensiones del unités derivat posse esser expresset in términos del dimensiones del unités basic.

Combinationes de basic e derivat unités posse esser usat a expresser altri derivat unités. Por exemple, li SI unité de [[fortie]] es li [[Newton (unité)|newton]] (N), li SI unité de [[pression]] es li [[Pascal (unité)|pascal]] (Pa)—e li pascal posse esser definit quam un newton per metre quadrat (N/m<sup>2</sup>).<ref>{{cite web |title=Units & Symbols for Electrical & Electronic Engineers |url=http://www.theiet.org/students/resources/units-symbols.cfm |publisher=Institution of Engineering and Technology |date=1996 |pages=8–11 |access-date=19 August 2013 | archive-url = https://web.archive.org/web/20130628212624/http://www.theiet.org/students/resources/units-symbols.cfm | archive-date = 28 June 2013}}</ref>

{| class="wikitable" style="margin:1em auto 1em auto;line-height:1.4"
|+ <big>SI unités derivat con special nómines e simboles</big><ref name="NIST330" />
|-
! scope="col" | Nómine
! scope="col" | Simbol
! scope="col" | Quantitá
! scope="col" | In SI unités basic
! scope="col" | In altri SI unités
|-
! scope="row" | [[radian]]<ref name=":0" group="N">Li radian e steradian es definat quam null dimensional unités derivat.</ref>
| style="text-align:center;"| rad
| [[angul|plani angul]]
| style="text-align:center;"| m/m
| style="text-align:center;"| 1
|-
! scope="row" | [[steradian]]<ref name=":0" group="N" />'''
| style="text-align:center;"| sr
| [[solid angul]]
| style="text-align:center;"| m<sup>2</sup>/m<sup>2</sup>
| style="text-align:center;"| 1
|-
! scope="row" | [[hertz]]
| style="text-align:center;"| Hz
| [[frequentie]]
| style="text-align:center;"| s<sup>−1</sup>
| <!-- intentionmen blanc -->
|-
! scope="row" | [[newton (unité)|newton]]
| style="text-align:center;"| N
| [[fortie]], [[pesa]]
| style="text-align:center;"| kg⋅m⋅s<sup>−2</sup>
| <!-- intentionmen blanc -->
|-
! scope="row" | [[pascal (unité)|pascal]]
| style="text-align:center;"| Pa
| [[pression]], [[Tension (mecanica)|tension]]
| style="text-align:center;"| kg⋅m<sup>−1</sup>⋅s<sup>−2</sup>
| style="text-align:center;"| N/m<sup>2</sup> = J/m<sup>3</sup>
|-
! scope="row" | [[joule]]
| style="text-align:center;"| J
| [[energie]], [[Labor mecanic|labor]], [[calore]]
| style="text-align:center;"| kg⋅m<sup>2</sup>⋅s<sup>−2</sup>
| style="text-align:center;"| N-m = Pa-m<sup>3</sup>
|-
! scope="row" | [[watt]]
| style="text-align:center;"| W
| [[Potentie (fisica)|potentie]], [[flution radiant]]
| style="text-align:center;"| kg⋅m<sup>2</sup>⋅s<sup>−3</sup>
| style="text-align:center;"| J/s
|-
! scope="row" | [[coulomb]]
| style="text-align:center;"| C
| [[electric charge]]
| style="text-align:center;"| s-A
| <!-- intentionmen blanc -->
|-
! scope="row" | [[volt]]
| style="text-align:center;"| V
| [[electric potentiale]], [[voltage]], [[Electromotiv fortie|emf]]
| style="text-align:center;"| kg⋅m<sup>2</sup>⋅s<sup>−3</sup>⋅A<sup>−1</sup>
| style="text-align:center;"| W/A = J/C
|-
! scope="row" | [[farad]]
| style="text-align:center;"| F
| [[capacitantie]]
| style="text-align:center;"| kg<sup>−1</sup>⋅m<sup>−2</sup>⋅s<sup>4</sup>⋅A<sup>2</sup>
| style="text-align:center;"| C/V = C<sup>2</sup>/J
|-
! scope="row" | [[ohm (unité)|ohm]]
| style="text-align:center;"| Ω
| [[electric resistantie|resistantie]], [[electric impedantie|impedantie]], [[Reactantie (electronica)|reactantie]]
| style="text-align:center;"| kg⋅m<sup>2</sup>⋅s<sup>−3</sup>⋅A<sup>−2</sup>
| style="text-align:center;"| V/A = J-s/C<sup>2</sup>
|-
! scope="row" | [[Siemens (unité)|siemens]]
| style="text-align:center;"| S
| [[electric conductantie|conductantie]]
| style="text-align:center;"| kg<sup>−1</sup>⋅m<sup>−2</sup>⋅s<sup>3</sup>⋅A<sup>2</sup>
| style="text-align:center;"| Ω<sup>−1</sup>
|-
! scope="row" | [[Weber (unité)|weber]]
| style="text-align:center;"| Wb
| [[magnetic flution]]
| style="text-align:center;"| kg⋅m<sup>2</sup>⋅s<sup>−2</sup>⋅A<sup>−1</sup>
| style="text-align:center;"| V-s
|-
! scope="row" | [[tesla (unité)|tesla]]
| style="text-align:center;"| T
| [[densitá de magnetic flution]]
| style="text-align:center;"| kg⋅s<sup>−2</sup>⋅A<sup>−1</sup>
| style="text-align:center;"| Wb/m<sup>2</sup>
|-
! scope="row" | [[henry (unité)|henry]]
| style="text-align:center;"| H
| [[inductantie]]
| style="text-align:center;"| kg⋅m<sup>2</sup>⋅s<sup>−2</sup>⋅A<sup>−2</sup>
| style="text-align:center;"| Wb/A
|-
! scope="row" | [[gradu Celsius]]
| style="text-align:center;"| °C
| [[temperatura]] relatent a 273,15 K
| style="text-align:center;"| K
| <!-- intentionmen blanc -->
|-
! scope="row" | [[lumen (unité)|lumen]]
| style="text-align:center;"| lm
| [[luminosi flution]]
| style="text-align:center;"| cd-sr
| style="text-align:center;"| cd-sr
|-
! scope="row" | [[lux]]
| style="text-align:center;"| lx
| [[illuminantie]]
| style="text-align:center;"| cd⋅sr⋅m<sup>−2</sup>
| style="text-align:center;"| lm/m<sup>2</sup>
|-
! scope="row" | [[becquerel]]
| style="text-align:center;"| Bq
| [[Radioactiv desintegration|activitá relatent a un radionuclid]] (desintegrationes per unit témpor)
| style="text-align:center;"| s<sup>−1</sup>
| <!-- intentionmen blanc -->
|-
! scope="row" | [[gray (unité)|gray]]
| style="text-align:center;"| Gy
| [[absorptet dose]] (de [[ionisant radiation]])
| style="text-align:center;"| m<sup>2</sup>⋅s<sup>−2</sup>
| style="text-align:center;"| J/kg
|-
! scope="row" | [[sievert]]
| style="text-align:center;"| Sv
| [[equivalent dose]] (de [[ionisant radiation]])
| style="text-align:center;"| m<sup>2</sup>⋅s<sup>−2</sup>
| style="text-align:center;"| J/kg
|-
! scope="row" | [[katal]]
| style="text-align:center;"| kat
| [[catalitic activitá]]
| style="text-align:center;"| mol⋅s<sup>−1</sup>
| <!-- intentionmen blanc -->
|-
| colspan="5" |'''Notes'''
<references group="N" />
|}

{| class="wikitable" style="margin:1em auto 1em auto;line-height:1.4"
|+ <big>Exemples de coherent unités derivat in terminos de unités basic</big><ref name="NIST330" />
|-
! scope="col" | Nómine
! scope="col" | Simbol
! scope="col" | Quantitá derivat
! scope="col" | Tipic simbol
|-
! scope="row" | [[metre quadrat]]
| style="text-align:center;"| m<sup>2</sup>
| [[area]]
| style="text-align:center;"| ''A''
|-
! scope="row" | [[metre cubic]]
| style="text-align:center;"| m<sup>3</sup>
| [[volume]]
| style="text-align:center;"| ''V''
|-
! scope="row" | [[metre per seconde]]
| style="text-align:center;"| m/s
| [[rapiditá]], [[velocitá]]
| style="text-align:center;"| ''v''
|-
! scope="row" | [[metre per seconde quadrat]]
| style="text-align:center;"| m/s<sup>2</sup>
| [[acceleration]]
| style="text-align:center;"| ''a''
|-
! scope="row" rowspan="2" | [[reciproc metre]]
| rowspan="2" style="text-align:center;"| m<sup>−1</sup>
| [[númere de unde]]
| style="text-align:center;"| ''σ'', ''ṽ''
|-
| [[vergentie (optica)]]
| style="text-align:center;"| ''V'', 1/''f''
|-
! scope="row" | [[kilogramme per metre cubic]]
| style="text-align:center;"| kg/m<sup>3</sup>
| [[densitá]]
| style="text-align:center;"| ''ρ''
|-
! scope="row" | kilogram per metre quadrat
| style="text-align:center;"| kg/m<sup>2</sup>
| [[superficial densitá]]
| style="text-align:center;"| ''ρ''<sub>A</sub>
|-
! scope="row" | metre cubic per kilogramme
| style="text-align:center;"| m<sup>3</sup>/kg
| [[specific volume]]
| style="text-align:center;"| ''v''
|-
! scope="row" | ampere per metre quadrat
| style="text-align:center;"| A/m<sup>2</sup>
| [[current densitá]]
| style="text-align:center;"| ''j''
|-
! scope="row" | [[Amperes per metre|ampere per metre]]
| style="text-align:center;"| A/m
| [[campe magnetic|intensitá de campe magnetic]]
| style="text-align:center;"| ''H''
|-
! scope="row" | mole per metre cubic
| style="text-align:center;"| mol/m<sup>3</sup>
| [[concentration]]
| style="text-align:center;"|''c''
|-
! scope="row" | [[kilogramme per metre cubic]]
| style="text-align:center;"| kg/m<sup>3</sup>
| [[Concentration de masse (chimie)|concentration de masse]]
| style="text-align:center;"| ''ρ'', ''γ''
|-
! scope="row" | [[candela per metre quadrat]]
| style="text-align:center;"| cd/m<sup>2</sup>
| [[luminantie]]
| style="text-align:center;"| ''L''<sub>v</sub>
|}

{| class="wikitable" style="margin:1em auto 1em auto;line-height:1.4"
|+ <big>Exemples de unités derivat que include unités con special nómines</big><ref name="NIST330" />
|-
! scope="col" | Nómine
! scope="col" | Simbol
! scope="col" | Quantitá
! scope="col" | In SI unités basic
|-
! scope="row" | [[pascal-seconde]]
| style="text-align:center;"| Pa⋅s
| [[dinamic viscositá]]
| style="text-align:center;"| m<sup>−1</sup>⋅kg⋅s<sup>−1</sup>
|-
! scope="row" | [[newton-metre]]
| style="text-align:center;"| N⋅m
| [[momente de fortie]]
| style="text-align:center;"| m<sup>2</sup>⋅kg⋅s<sup>−2</sup>
|-
! scope="row" | newton per metre
| style="text-align:center;"| N/m
| [[superficial tension]]
| style="text-align:center;"| kg⋅s<sup>−2</sup>
|-
! scope="row" | [[radian per seconde]]
| style="text-align:center;"| rad/s
| [[angulari velocitá]], [[angulari frequentie]]
| style="text-align:center;"| s<sup>−1</sup>
|-
! scope="row" | [[radian per seconde quadrat]]
| style="text-align:center;"| rad/s<sup>2</sup>
| [[angulari acceleration]]
| style="text-align:center;"| s<sup>−2</sup>
|-
! scope="row" | [[watt per metre quadrat]]
| style="text-align:center;"| W/m<sup>2</sup>
| densitá de caloric flution, [[irradiantie]]
| style="text-align:center;"| kg⋅s<sup>−3</sup>
|-
! scope="row" | joule per kelvin
| style="text-align:center;"| J/K
| [[entropie]], [[caloric capacitá]]
| style="text-align:center;"| m<sup>2</sup>⋅kg⋅s<sup>−2</sup>⋅K<sup>−1</sup>
|-
! scope="row" | joule per kilogram-kelvin
| style="text-align:center;"| J/(kg⋅K)
| [[specific caloric capacitá]], [[specific entropie]]
| style="text-align:center;"| m<sup>2</sup>⋅s<sup>−2</sup>⋅K<sup>−1</sup>
|-
! scope="row" | joule per kilogram
| style="text-align:center;"| J/kg
| [[specific energie]]
| style="text-align:center;"| m<sup>2</sup>⋅s<sup>−2</sup>
|-
! scope="row" | watt per metre-kelvin
| style="text-align:center;"| W/(m⋅K)
| [[termic conductivitá]]
| style="text-align:center;"| m⋅kg⋅s<sup>−3</sup>⋅K<sup>−1</sup>
|-
! scope="row" | joule per metre cubic
| style="text-align:center;"| J/m<sup>3</sup>
| [[energic densitá]]
| style="text-align:center;"| m<sup>−1</sup>⋅kg⋅s<sup>−2</sup>
|-
! scope="row" | volt per metre
| style="text-align:center;"| V/m
| [[intensitá de campe electric]]
| style="text-align:center;"| m⋅kg⋅s<sup>−3</sup>⋅A<sup>−1</sup>
|-
! scope="row" | coulomb per metre cubic
| style="text-align:center;"| C/m<sup>3</sup>
| [[densitá de charge electric]]
| style="text-align:center;"| m<sup>−3</sup>⋅s⋅A
|-
! scope="row" | coulomb per metre quadrat
| style="text-align:center;"| C/m<sup>2</sup>
| [[superficial densitá de charge]], [[densitá de electric flution]], [[electric deplazzament]]
| style="text-align:center;"| m<sup>−2</sup>⋅s⋅A
|-
! scope="row" | farad per metre
| style="text-align:center;"| F/m
| [[permittivitá]]
| style="text-align:center;"| m<sup>−3</sup>⋅kg<sup>−1</sup>⋅s<sup>4</sup>⋅A<sup>2</sup>
|-
! scope="row" | henry per metre
| style="text-align:center;"| H/m
| [[Permeabilitá (electromagnetisme)|permeabilitá]]
| style="text-align:center;"| m⋅kg⋅s<sup>−2</sup>⋅A<sup>−2</sup>
|-
! scope="row" | joule per mole
| style="text-align:center;"| J/mol
| [[Joule per mole|molari energie]]
| style="text-align:center;"| m<sup>2</sup>⋅kg⋅s<sup>−2</sup>⋅mol<sup>−1</sup>
|-
! scope="row" | joule per mole-kelvin
| style="text-align:center;"| J/(mol⋅K)
| [[molari entropie]], [[molari caloric capacitá]]
| style="text-align:center;"| m<sup>2</sup>⋅kg⋅s<sup>−2</sup>⋅K<sup>−1</sup>⋅mol<sup>−1</sup>
|-
! scope="row" | coulomb per kilogramme
| style="text-align:center;"| C/kg
| [[Radiational exposition|exposition]] (X- e γ-radies)
| style="text-align:center;"| kg<sup>−1</sup>⋅s⋅A
|-
! scope="row" | gray per seconde
| style="text-align:center;"| Gy/s
| [[rate de absorptet dose]]
| style="text-align:center;"| m<sup>2</sup>⋅s<sup>−3</sup>
|-
! scope="row" | watt per steradian
| style="text-align:center;"| W/sr
| [[radiant intensitá]]
| style="text-align:center;"| m<sup>2</sup>⋅kg⋅s<sup>−3</sup>
|-
! scope="row" | watt per metre quadrat-steradian
| style="text-align:center;"| W/(m<sup>2</sup>⋅sr)
| [[radiantie]]
| style="text-align:center;"| kg⋅s<sup>−3</sup>
|-
! scope="row" | katal per metre cubic
| style="text-align:center;"| kat/m<sup>3</sup>
| [[concentration de catalitic activitá]]
| style="text-align:center;"| m<sup>−3</sup>⋅s<sup>−1</sup>⋅mol
|}

=== Unités sin dimension ===
Li unité de un [[quantitá sin dimension]] es [[un]] (simbol 1), ma it es monstrat rarmen.<ref>{{SIbrochure9th|page=136}}</ref> 
Li radian e steradian es anc quantitás sin dimension, ma ili usa li simboles rad e sr, proprimen.<ref>{{SIbrochure9th|page=137}}</ref>

==Prefixes==
[[Metric prefixe]]s es addit al nómines de unités a producte multiplicas e [[submultiplica]]s del original unité. Omni metric prefixes es integral multiplicas de deci, e supra un cent o infra un centisime, ili es integral multiplicas de un mill. Por exemple, ''kilo-'' denota un multiplica de un mill e ''milli-'' denota un multiplica de un millisime, talmen hay un mill millimetres in un metre e un mill metres in un kilometre. Li prefixes es nequande combinat; p.ex., li millionesime de un metre es un ''micrometre'', ne un ''millimillimetre''. Li multiplicas de li kilogramme es nominat quam si li gramme esset li basic unité, e un millionesime de un kilogramme es un ''milligramme'', ne un ''microkilogramme''.<ref name="SIBrochure"/><ref name="NIST811">{{cite book |author-first1=Ambler |author-last1=Thompson |author-first2=Barry N. |author-last2=Taylor |date=2008 |url=http://physics.nist.gov/cuu/pdf/sp811.pdf |title=Guide for the Use of the International System of Units (SI) (Special publication 811) |location=Gaithersburg, MD |publisher=[[National Institute of Standards and Technology]]}}</ref> Quande prefixes es usat de formar multiplicas e submultiplicas de SI basic e derivat unités, li resultant unités ne es coherent.<ref name="SIBrochure"/>

Li BIPM specifica 24 metric prefixes:

{| class="wikitable" style="padding: 0; text-align: center; width: 0"
|+ <big>Li SI Prefixes</big>
|-
! colspan=2| Prefixe !! rowspan=2| Base 10
! rowspan=2| [[Decimal]]<!-- equivalente in [[SI#SI scritional stil|SI scritional stil]] -->
! rowspan=2| Adoption<br/><ref group="nb">Prefixes adoptet ante 1960 ja existet ante SI. Li introduction del [[centimetre–gramme–seconde sistema de unites|CGS sistema]] esset ye 1873.</ref>
|-
! Nómine !! Simbol
|-
| quetta || Q || style="text-align:left;"| [[Ordines de grandesse (númere)#1030|10<sup>30</sup>]]
| style="text-align:right; font-variant-numeric: tabular-nums;"| 1.000.000.000.000.000.000.000.000.000.000 || rowspan=2| 2022<ref name="newUnitAdoption">{{cite web |title=On the extension of the range of SI prefixes |url=https://www.bipm.org/en/cgpm-2022/resolution-3 |date=18 November 2022 |access-date=5 February 2023 }}</ref> 
|-
| ronna || R || style="text-align:left;"| [[Ordines de grandesse (númere)#1027|10<sup>27</sup>]]
| style="text-align:right; font-variant-numeric: tabular-nums;"| 1.000.000.000.000.000.000.000.000.000 
|-
| yotta || Y || style="text-align:left;"| [[Ordines de grandesse (númere)#1024|10<sup>24</sup>]]
| style="text-align:right; font-variant-numeric: tabular-nums;"| 1.000.000.000.000.000.000.000.000}} || rowspan=2|1991 
|-
| zetta || Z || style="text-align:left;"| [[Ordines de grandesse (númere)#1021|10<sup>21</sup>]]
| style="text-align:right; font-variant-numeric: tabular-nums;"| 1.000.000.000.000.000.000.000
|-
| exa || E || style="text-align:left;"| [[Ordines de grandesse (númere)#1018|10<sup>18</sup>]]
| style="text-align:right; font-variant-numeric: tabular-nums;"| 1.000.000.000.000.000.000 ||rowspan=2| 1975 
|-
| peta || P || style="text-align:left;"| [[Ordines de grandesse (númere)#1015|10<sup>15</sup>]]
| style="text-align:right; font-variant-numeric: tabular-nums;"| 1.000.000.000.000.000
|-
| tera || T || style="text-align:left;"| [[Ordines de grandesse (númere)#1012|10<sup>12</sup>]]
| style="text-align:right; font-variant-numeric: tabular-nums;"| 1.000.000.000.000 ||rowspan=2| 1960 
|-
| [[giga-|giga]] || G || style="text-align:left;"| [[1.000.000.000|10<sup>9</sup>]]
| style="text-align:right; font-variant-numeric: tabular-nums;"| 1.000.000.000
|-
| [[mega-|mega]] || M || style="text-align:left;"| [[1.000.000|10<sup>6</sup>]]
| style="text-align:right; font-variant-numeric: tabular-nums;"| 1.000.000 || 1873 
|-
| [[kilo-|kilo]] || k || style="text-align:left;"| [[1000 (númere)|10<sup>3</sup>]]
| style="text-align:right; font-variant-numeric: tabular-nums;"| 1.000 ||rowspan=3| 1795 
|-
| [[hecto-|hecto]] || h || style="text-align:left;"| [[100|10<sup>2</sup>]] || style="text-align:right; font-variant-numeric: tabular-nums;"| 100
|-
| [[deca-|deca]] || da || style="text-align:left;"| [[10|10<sup>1</sup>]] || style="text-align:right; font-variant-numeric: tabular-nums;"| 10
|- style="background:#EAECF0;color:black;"
| — || — || style="text-align:left;"| [[1|10<sup>0</sup>]] || style="font-variant-numeric: tabular-nums;"| 1 || —
|-
| [[deci-|deci]] || d || style="text-align:left;"| [[Ordines de grandesse (númere)#10-1|10<sup>−1</sup>]]
| style="text-align:left; font-variant-numeric: tabular-nums;"| 0,1 ||rowspan=3| 1795 
|-
| [[centi-|centi]] || c || style="text-align:left;"| [[Ordines de grandesse (númere)#10−2|10<sup>−2</sup>]]
| style="text-align:left; font-variant-numeric: tabular-nums;"| 0,01
|-
| [[milli-|milli]] || m || style="text-align:left;"| [[Ordines de grandesse (númere)#10−3|10<sup>−3</sup>]]
| style="text-align:left; font-variant-numeric: tabular-nums;"| 0,001
|-
| [[micro-|micro]] || μ || style="text-align:left;"| [[Ordines de grandesse (númere)#10−6|10<sup>−6</sup>]]
| style="text-align:left; font-variant-numeric: tabular-nums;"| 0,000.001 || 1873 
|-
| [[nano-|nano]] || n || style="text-align:left;"| [[Ordines de grandesse (númere)#10−9|10<sup>−9</sup>]]
| style="text-align:left; font-variant-numeric: tabular-nums;"| 0,000.000.001 ||rowspan=2| 1960 
|-
| pico || p || style="text-align:left;"| [[Ordines de grandesse (númere)#10−12|10<sup>−12</sup>]]
| style="text-align:left; font-variant-numeric: tabular-nums;"| 0,000.000.000.001 
|-
| femto || f || style="text-align:left;"| [[Ordines de grandesse (númere)#10−15|10<sup>−15</sup>]]
| style="text-align:left; font-variant-numeric: tabular-nums;"| 0,000.000.000.000.001 ||rowspan=2| 1964 
|-
| atto || a || style="text-align:left;"| [[Ordines de grandesse (númere)#10−18|10<sup>−18</sup>]]
| style="text-align:left; font-variant-numeric: tabular-nums;"| 0,000.000.000.000.000.001
|-
| zepto || z || style="text-align:left;"| [[Ordines de grandesse (númere)#10−21|10<sup>−21</sup>]]
| style="text-align:left; font-variant-numeric: tabular-nums;"| 0,000.000.000.000.000.000.001}} ||rowspan=2| 1991 
|-
| yocto || y || style="text-align:left;"| [[Ordines de grandesse (númere)#10−24|10<sup>−24</sup>]]
| style="text-align:left; font-variant-numeric: tabular-nums;"| 0,000.000.000.000.000.000.000.001
|-
| ronto || r || style="text-align:left;"| [[Ordines de grandesse (númere)#10−27|10<sup>−27</sup>]]
| style="text-align:left; font-variant-numeric: tabular-nums;"| 0,000.000.000.000.000.000.000.000.001 ||rowspan=2| 2022<ref name="newUnitAdoption"/>
|-
| quecto || q || style="text-align:left;"| [[Ordines de grandesse (númere)#10−30|10<sup>−30</sup>]]
| style="text-align:left; font-variant-numeric: tabular-nums;"| 0,000.000.000.000.000.000.000.000.000.001
|-
| style="text-align: left;" colspan=5 |
;Notes
{{reflist|group=nb}}
|}<noinclude>
{{documentation}}
</noinclude>

==Non-SI unités acceptat por usu con SI==

Multi non-SI unités continua esser usat in li scientific, tecnic, e comercial publicationes. Alcun unités es profundmen fixat in historie e cultura, e lor usu ne have esset viceat completmen per lor SI alternatives. Li CIPM recognisat tal traditiones per compilar un liste del [[non-SI unités acceptat por usu con SI]]:<ref name="SIBrochure"/>

[[File:CubeLitre.svg|right|thumb|upright=1.1|Benque ne un unité del SI, li litre mey esser usat con SI unités. It es equivalent a (10&nbsp;cm)<sup>3</sup>&nbsp;=&nbsp;(1&nbsp;dm)<sup>3</sup>&nbsp;=&nbsp;10<sup>−3</sup>&nbsp;m<sup>3</sup>.]]

Some unités de témpor, angul, e ancian non-SI unités have un long historie de usu. Max mult societás have usat li solari [[die]] e su nondecimal subdivisiones quam un base de témpor e, ne quam li [[Pede (unité)|pede]] o li [[Pund (masse)|pund]], tis esset li sam sin regarde de u ili es mesurat. Li [[radian]], pro que it es 1/2{{pi}} de un revolution, have matematic avantages, ma it es usat rarmen por navigation. Adplu, li unités usat in navigation partú in li munde es simil. Li [[tonne]], [[litre]], e [[hectare]] esset adoptat per li CGPM in 1879 e have esset retenet quam unités que mey esser usat junt con SI unités, pro que ili esset simboles unic. Li acceptat non-SI unités es dat infra:

{| class="wikitable"
|+ Non-SI unités acceptat por usu con SI unités
|-
! scope="col" | [[Fisic quantitá|Quantitá]]
! scope="col" | Nómine
! scope="col" | [[Simbol]]
! scope="col" | Valore in SI unités
|-
|rowspan="3"| [[témpor]]
! scope="row" | [[minute]]
| min
| 1 min = 60 s
|-
! scope="row" | [[hor]]
| h
| 1 h = 60 min = 3600 s 
|-
! scope="row" | [[die]]
| d
| 1 d = 24 h = 86.400 s 
|-
| [[longore]]
! scope="row" | [[unité astronomic]]
| UA
| 1 UA = 149.597.870.700 m
|-
|rowspan="3"| [[Angul|angul del plane e<br />fasa]]
! scope="row" | [[Gradu (angul)|gradu]]
| °
| 1° = {{pi}}/180 rad
|-
! scope="row" | [[Minute e seconde de arc|arcminute]]
| ′
| 1′ = 1/60° = {{pi}}/10.800 rad 
|-
! scope="row" | [[Minute e seconde de arc|arcseconde]]
| ″
| 1″ = 1/60′ = {{pi}}/648.000 rad
|-
| [[area]]
! scope="row" | [[hectare]]
| ha
| 1 ha = 1 hm<sup>2</sup> = 10<sup>4</sup> m<sup>2</sup>
|-
| [[volume]]
! scope="row" | [[litre]]
| l, L
| 1 l = 1 L = 1 dm<sup>3</sup> = 10<sup>3</sup> cm<sup>3</sup> = 10<sup>−3</sup> m<sup>3</sup>
|-
|rowspan="2"| [[masse]]
! scope="row" | [[tonne]] (metric tonne)
| t
| 1 t = 1 Mg = 10<sup>3</sup> kg
|-
! scope="row" | [[dalton (unité)|dalton]]
| Da
| 1 Da = 1,660539040 x 10<sup>-27</sup> kg
|-
| [[energie]]
! scope="row" | [[electronvolt]]
| eV
| 1 eV = 1,602176634 x 10<sup>-19</sup> J}
|-
|rowspan="3"| quantitás de proportion <br />logaritmic
! scope="row" | [[neper]]
| Np
|rowspan="3"| <small>Quande usar ti unités, it es important que li natura del quantitá es specificat e li referential valore usat es specificat.</small>
|-
! scope="row" | bel
| B
|-
! scope="row" | [[decibel]]
| dB
|}
Ti unités es usat in combination con SI unités in comun unités quam li kilowatt-hor (1&nbsp;kW-h = 3.6&nbsp;MJ).

==Sistema International de Quantitás==
Li quantitás e equationes que provide li contextu in quel li SI unités es definit es nu refere a quam li ''[[Sistema International de Quantitás]]'' (SIQ).
Li SIQ es basat sur li [[Quantitá|quantitás]] conform a chascun del [[SI unités basic|sett basic unités del SI]]. Altri quantitás, quam [[area]], [[pression]], e [[electric resistantie]], es derivat ex ti basic quantitás per clar equationes. Li SIQ defini li quantitás que es mesurat con li SI unités.<ref>{{cite book |title=International vocabulary of metrology – Basic and general concepts and associated terms (VIM) |date=2012 |publisher=International Bureau of Weights and Measures (BIPM): Joint Committee for Guides in Metrology |edition=3rd |chapter-url=http://www.bipm.org/utils/common/documents/jcgm/JCGM_200_2012.pdf |access-date=28 March 2015 |chapter=1.16}}</ref> Li SIQ es formalisat, in parte, in li international standarde [[ISO/IEC 80000]], quel esset complete in 2009 con li publication de [[ISO 80000-1]],<ref>S. V. Gupta, ''Units of Measurement: Past, Present and Future. International System of Units'', p.&nbsp;16, Springer, 2009. {{ISBN|3642007384}}.</ref> e esset reviset in 2019–2020.

==Realisation de unités==
[[File:Silicon sphere for Avogadro project.jpg|thumb|upright|Silicium sfere por li [[Avogadro projecte]] usat por mesurar li constante de Avogadro al relativ [[standard incertita]] de 2 x 10<sup>−8</sup> o minu<ref>{{cite web |title=Avogadro Project |url=http://www.npl.co.uk/science-technology/mass-and-force/research/avogadro-project |publisher=National Physical Laboratory |access-date=19 August 2010}}</ref>]]

Metrologistes distinte atentivmen inter li definition de un unité e su [[Realisation (metrologie)|realisation]]. Li definition de chascun basic unité del SI es specificar talmen it es unic e provide un bon base teoretic por far li max acurat e reproductibil mesurationes. Li realisation del definition de un unité es li procedura per quel li definition posse esser usat de constatar li valore e associat íncertitá de un quantitá del sam tip quam li unité.

==Comun notiones del metric unités==

Li basic unités del metric sistema, quam originalmen definit, representat comun quantitás o proportiones de natura. Ili ancor fa – li modern precismen definit quantitás es ameliorationes de definition e metodologie, ma ancor con li sam dimensiones. In casus u experimental precision mey ne esser necessi o obtenibil, o u aproximationes es satisfatori, li original definitiones posse esser usat. Alcun exemples:

*Un seconde es 1/60 de un minute, quel es 1/60 de un hor, quel es 1/24 de un die, e talmen un seconde es 1/86.400 de un die (li usu de base 60 es de ancian [[Babilon]]); un seconde es li temporal duration por un cose a cader libermen 4,9 metres ex repose.
*Li longore del [[equator]] es presc 40.000.000 metres (plu precismen 40.075.014,2 metres).<ref>{{cite web|url=https://www.space.com/17638-how-big-is-earth.html|title=How Big Is Earth?|last1=Science|first1=Tim Sharp 2017-09-15T15:47:00Z|last2=Astronomy|website=Space.com|access-date=22 October 2019}}</ref> In facte, li dimensiones del [[Terra]] esset usat per li Academie Francesi in li original definition del metre.<ref>{{cite web|url=https://www.britannica.com/science/metre-measurement|title=Metre {{!}} measurement|website=Encyclopedia Britannica|access-date=22 October 2019}}</ref>
*Li metre es presc li longore de [[Secondic pendul|un pendul que have un periode de 2 secondes]].
*Li kilogramme es li masse de un litre de [[aqua]] frigid; un cubic centimetre (millilitre) de aqua have un masse de un gramme.
*Un candela es circa li intensitá luminosi de un moderatmen brilliant candel, o 1 candel-potentie; un 60&nbsp;W [[incandescent ampulle electric]] have un intensitá luminosi de circa 64 candelas.<ref>{{cite web|title=Lumens and the Lighting Facts Label|url=https://www.energy.gov/energysaver/save-electricity-and-fuel/lighting-choices-save-you-money/lumens-and-lighting-facts|access-date=11 June 2020|website=Energy.gov|language=en}}</ref>
*Un mole de un substantie have un masse que es su [[masse moleculari]] expresset in unités de grammes; li masse de un mole de [[carbon]] es 12,0&nbsp;g, de li masse de un mole de comun sale es 58,4&nbsp;g.
*Pro que omni [[gas|gases]] have li sam volume per mole a un dat temperatura e pression, ne proxim lor punctus de liquefaction e solidification (vide [[Perfect gas]]), and aere es circa 1/5 [[oxigen]] (moleculari masse 32) e 4/5 [[nitrogen]] (moleculari masse 28), li aproximativ densitá de un quasi-perfect gas relatent a aere posse esser obtenet per divider su masse moleculari per 29. Por exemple, [[carbon monoxid]] (moleculari masse 28) have presc li sam densitá quam aere.
*Un diferentie de temperatura de un kelvin es li sam quam un gradu Celsius: 1/100 del diferentie de temperatura inter li puntus gelant e bollint de aqua al nivelle del mare; li temperatura absolut in kelvins es li temperatura in gradus Celsius plus circa 273; li [[temperatura del córpor human]] es circa 37&nbsp;°C or 310&nbsp;K.
*Un 60&nbsp;W incandescent ampulle electric a 120&nbsp;V (US domestic voltage) consuma 0,5&nbsp;A. Un 60&nbsp;W ampulle electric a 230&nbsp;V (Europan voltage) consuma 0,26&nbsp;A.

==Vide anc==
* [[Conversion de unités]]
* [[Non-SI unités acceptat por usu con SI unités]]
* [[Sistemas de mesuration]]
* [[Universal Témpor Coordinat]] (UTC) 

==Referenties==
<references/>

[[Categorie:Sistema International de Unités]]
[[Categorie:Sistemas de unités]]
[[Categorie:Standardes international]]