For questions related to volume, the amount of space that a substance or object occupies.

**Volume** is the quantity of three-dimensional space occupied by a liquid, solid, or gas.

Common units used to express volume include liters, cubic meters, gallons, milliliters, teaspoons, and ounces, though many other units exist.

**Volume vs. Mass**

Volume is the amount of space occupied by a substance, while mass is the amount of matter it contains. The amount of mass per unit of volume is a sample's density.

**Capacity in Relation to Volume**

Capacity is the measure of the content of a vessel that holds liquids, grains, or other materials that take the shape of the container. Capacity is not necessarily the same as volume. It is always the interior volume of the vessel. Units of capacity include the liter, pint, and gallon, while the unit of volume (SI) is derived from a unit of length.

**In differential geometry**, a branch of mathematics, a volume form on a differentiable manifold is a differential form of top degree (i.e., whose degree is equal to the dimension of the manifold) that is nowhere equal to zero. A manifold has a volume form if and only if it is orientable. An orientable manifold has infinitely many volume forms, since multiplying a volume form by a non-vanishing function yields another volume form. On non-orientable manifolds, one may instead define the weaker notion of a density. Integrating the volume form gives the volume of the manifold according to that form.

**In thermodynamics,** the volume of a system is an important extensive parameter for describing its thermodynamic state. The specific volume, an intensive property, is the system's volume per unit of mass. Volume is a function of state and is interdependent with other thermodynamic properties such as pressure and temperature. For example, volume is related to the pressure and temperature of an ideal gas by the ideal gas law.

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