International System of Units
The modern metric system used worldwide for measurement.
The International System of Units, known by the abbreviation SI (from its official French name, Système international d'unités), is the modern form of the metric system and the world's most widely used system of measurement. It is the only system of measurement with official status in nearly every country in the world, employed in science, technology, industry, and everyday commerce. The International Bureau of Weights and Measures (BIPM) coordinates the SI.
Lore & Background
The SI also provides 24 prefixes that, when added to the name and symbol of a coherent unit, produce decimal multiples and submultiples.
Reader's Guide
The International System of Units is significant as the world's most widely used system of measurement, with official status in nearly every country. It provides a coherent and decimal-based framework for science, technology, industry, and everyday commerce. The current definition relies on seven defining constants—fundamental constants of nature such as the speed of light and the Planck constant—rather than physical artefacts, allowing for more precise and stable realizations that can improve with scientific advancement. Its coordination by the BIPM ensures global standardization, and its coherent nature means that equations between numerical values have the same form as those between physical quantities, simplifying scientific work.
Did You Know?
- The SI is based on seven defining constants, including the speed of light and the Planck constant.
Frequently Asked Questions
Who is International System of Units?
The International System of Units (SI) is the modern form of the metric system and the world's most widely adopted framework for measurement. It holds official legal status in nearly every country and is coordinated by the International Bureau of Weights and Measures (BIPM).
What are International System of Units's powers/role?
SI defines seven base units plus a set of 24 prefixes that let a single quantity scale from 10⁻³⁰ to 10³⁰, giving scientists, engineers, and everyday users one consistent language for measurement. It underpins all of science, technology, industry, and global commerce.
Why is International System of Units important?
It is the only measurement system with official legal standing in virtually every nation, making it the universal reference for research, trade, and engineering. Without a single shared framework, international collaboration and commerce would constantly clash over incompatible units.
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