volume

Volume is the amount of space that an object or substance occupies.

• Liquids are measured in litres or millilitres using a measuring cylinder, while the volume of a regular solid — like a cuboid-shaped notebook — can be calculated directly from length × width × height.
• Irregular objects, like a stone, don't fit a neat formula, so their volume is instead found by water displacement: lowering the object into a partly filled measuring cylinder and reading how much the water level rises.
• Reading a liquid's volume accurately means checking the meniscus — the curved surface liquids form in a narrow container — at the bottom for clear liquids and the top for coloured ones.
• Volume is the other half of the density formula: the same mass squeezed into a smaller volume produces a higher density, which is exactly why compressing a gas increases how dense it is.