SI base units
Seven named base units organize the SI quantity system.
Key knowledge
The SI base units are second (s), metre (m), kilogram (kg), ampere (A), kelvin (K), mole (mol) and candela (cd), for time, length, mass, electric current, thermodynamic temperature, amount of substance and luminous intensity respectively.
Conditions and scope
- Unit symbols are case-sensitive.
- Base units do not imply that other quantities or coherent derived units are less physically important.
Sources · 3
References
Sources retain their recorded scope. A source link alone does not establish verification of every statement.
Bureau International des Poids et Mesures (BIPM)2 sources
- 国際単位系(SI)第9版 · Japanese translation, V3.01National Metrology Institute of Japan, AISTReference guide · PDF
Evidence and review
SI Brochure 2.3.1, Table 2.
2026-10-10 · Seven names, symbols and associated base quantities only; practical realizations are outside scope.
Foundational review
2026-10-10 · Fresh primary-source inspection of the complete compact record, including every statement, equation, quantity and material condition, followed by independent AI editorial review. This check does not certify all linked lessons or every passage of every cited publication.
Sources from other places
Agreement within this scope
SI distinguishes seven base quantities and units, defined through fixed constants.
Unit and prefix capitalization matters; the seven definitions share the BIPM standard.
National Metrology Institute of Japan, AIST
- 国際単位系(SI)第9版 · Japanese translation, V3.01 JapanJapaneseShared standard
2.3.1 Definitions of SI base units, printed pp14–20
- 国際単位系(SI)第9版 · Japanese translation, V3.01
Entry details
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