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Physics vocabulary · Measurement and Units

SI units

Meaning in physics, with examples

nounCore term

In physics, SI units means: The international system of measurement units used in science, based on seven base units such as the metre, kilogram, second, ampere and kelvin. SI comes from the French 'Système international'.

In Turkish: SI birimleri, Uluslararası Birim Sistemi

How it is used

Teachers insist on SI units in calculations: convert grams to kilograms and centimetres to metres before putting numbers into a formula. Derived units such as the newton, joule and watt are built from the base units. Say 'S-I units', letter by letter.

Example sentences

  1. Give all your answers in SI units, so convert 250 g to 0.25 kg first.

  2. The joule is a derived SI unit equal to one newton metre.

Common collocations

  • SI base units
  • derived SI unit
  • convert to SI units
  • SI prefix
  • scientific notationA way of writing very large or very small numbers as a number between 1 and 10 multiplied by a power of ten, for example 3.0 × 10⁸ instead of 300,000,000.
  • dimensional analysisA method of checking or building an equation by comparing the units or basic dimensions (mass, length, time and so on) on each side. Both sides of a valid equation must match.
  • significant figuresThe digits in a number that carry real information about its precision, counted from the first non-zero digit. For example, 0.00450 has three significant figures.
  • massThe amount of matter in an object, which also measures how hard it is to change the object's motion. It is measured in kilograms (kg) and does not depend on location.
  • scalarA quantity that has size (magnitude) but no direction, such as mass, time, temperature, energy or speed. Scalars are added like ordinary numbers.

More terms: Measurement and Units

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