SI Meaning in the Cambridge English Dictionary
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Meaning of “SI” in the English Dictionary

"SI" in British English

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SInoun [U]

uk   us   /esˈaɪ/ specialized
abbreviation for Système International: the ​internationalsystem of ​units used for ​scientificmeasurements, with ​standardbaseunits such as the ​metre and the ​kilogram: The SI unit of ​electriccurrent is the ​ampere.
(Definition of SI from the Cambridge Advanced Learner’s Dictionary & Thesaurus © Cambridge University Press)

"SI" in American English

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SInoun [U]

science abbreviation forInternational System of Units (= an ​internationalsystem of ​units used for ​measurement in ​scientificwork)
(Definition of SI from the Cambridge Academic Content Dictionary © Cambridge University Press)

"SI" in Business English

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uk   us   /ˌesˈaɪ/ MEASURES
abbreviation for Système International: a ​system of ​units of ​measurement used ​internationally. SI ​unitsinclude the ​metre, ​kilogram, second, ampere (= ​unit of electric ​current), candela (= ​unit of ​light), kelvin (= ​unit of temperature), and the mole (= ​unit of the ​amount of a substance): The ​chartshows you how to ​convert from a ​conventionalunit to an SI ​unit.
UK LAW →  statutory instrument
(Definition of SI from the Cambridge Business English Dictionary © Cambridge University Press)
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