Is volume a si unit

Answer 1

Volume is the cube of the length, just as area is the square of the length.

For the same reasons (avoiding multiplicity of units which are not basic or fundamental quantities) that no separate UoM is devised for Area, nor for Volume.

SI established basic Units of Measurement (AKA: UoM) of dimensions such as mass, length and time, and then defined other "derived" units in terms of the basic dimensions in those units.

Instead of using the litre, SI uses the m3 (or dm3 as an equivalent to the litre) as UoM for volume.

Litre is still permitted to be used only for measurement of liquids where traditionally used (examples: oil, milk, etc). Its use UoM of capacity (size of empty space) is, however, deprecated.

In the case of volume, the basic dimension being length, volume is defined as (length)3.

In SI, the basic unit of length is defined as the metre, AKA: meter, (symbol: m), .

So, Unit of Measurement of volume is defined as the cubic metre (symbol: m3), or in terms of some other unit of length derived from the metre.

Examples:

Since, 1 m = 100 cm.

Therefore: 1 m3 = 1,000,000 cm3, (AKA: cc or ccm, ml, mL or millilitre).

Since, 1 m = 1,000 mm.

Therefore: 1 m3 = 1,000,000,000 mm3, (AKA: cmm, cubic millilitre, µl, µL, microlitre).

1 cm3 = 1,000 mm3, AKA: cmm, µl and µL.

1 cm3 = 1/1,000 dm3 = 1/1,000 l = 1/1,000 L = 1/1,000,000 m3.

1 m3 = 1,000 dm3, AKA: litre, l, liter, and L.

One could define a basic set of units based on mass, volume and time, instead of mass, length, and time; but then you would have to define unit of length as the cube root of the unit of volume, and unit of area as the square root of the cube root of the unit of volume. The awkwardness and practical inconvenience of this set is evident.

Answer 2

Volume is a measure of the space occupied by a 3 dimensional object.

Volume is measured in cubic units, eg cubic centimetres (= millilitres), cubic metres, cubic inches, cubic feet, etc.