Physical Quantity - Base Quantities

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).

International System of Units base quantities
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.

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