Base Quantities
The seven base quantities of the International System of Quantities (ISQ) and their corresponding SI units and dimensions are listed in the following table. Other conventions may have a different number of fundamental units (e.g. the CGS and MKS systems of units).
| Quantity name/s | (Common) Quantity symbol/s | SI unit name | SI unit symbol | Dimension symbol |
|---|---|---|---|---|
| Length, width, height, depth | a, b, c, d, h, l, r, s, w, x, y, z | metre | m | |
| Time | t | second | s | |
| Mass | m | kilogram | kg | |
| Temperature | T, θ | kelvin | K | |
| Amount of substance, number of moles | n | mole | mol | |
| Electric current | i, I | ampere | A | |
| Luminous intensity | Iv | candela | Cd | |
| Plane angle | α, β, γ, θ, φ, χ | radian | rad | dimensionless |
| Solid angle | ω, Ω | steradian | sr | dimensionless |
The last two angular units; plane angle and solid angle are subsidiary units used in the SI, but treated dimensionless. The subsidiary units are used for convenience to differentiate between a truly dimensionless quantity (pure number) and an angle, which are different measurements.
Read more about this topic: Physical Quantity
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