# Volume

Volume is
the quantity of three-dimensional space enclosed by a closed surface, for
example, the space that a substance (solid, liquid, gas, or plasma) or shape
occupies or

contains. Volume is often quantified numerically using the SI
derived unit, the cubic metre. The volume of a container is generally
understood to be the capacity of the container, i. e. the amount of fluid (gas
or liquid) that the container could hold, rather than the amount of space the
container itself displaces.
Three
dimensional mathematical shapes are also assigned volumes. Volumes of some
simple shapes, such as regular, straight-edged, and circular shapes can be
easily calculated using arithmetic formulas. Volumes of a complicated shape can
be calculated by integral calculus if a formula exists for the shape's
boundary. Where a variance in shape and volume occurs, such as those that exist
between different human beings, these can be calculated using three-dimensional
techniques such as the Body Volume Index. One-dimensional figures (such as
lines) and two-dimensional shapes (such as squares) are assigned zero volume in
the three-dimensional space.

The volume
of a solid (whether regularly or irregularly shaped) can be determined by fluid
displacement. Displacement of liquid can also be used to determine the volume
of a gas. The combined volume of two substances is usually greater than the
volume of one of the substances. However, sometimes one substance dissolves in
the other and the combined volume is not additive.

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