Volume has several related meanings about size and space, plus one about sound:

The most common meaning describes how much space something takes up or how much it can hold. A large suitcase has more volume than a small one because it fits more stuff inside. When you measure the volume of a fish tank, you're calculating how much water it holds, usually in gallons or liters. In math class, you learn formulas to find the volume of shapes like cubes and spheres. A scientist might measure the volume of a liquid in milliliters, while a construction worker thinks about the volume of concrete needed to pour a foundation.

Volume also means one book in a set of books. A library might have all twenty volumes of an encyclopedia, with each volume covering different topics. The first volume of a fantasy trilogy sets up the story that continues in volumes two and three.

The word also refers to how loud something is. When you turn up the volume on a speaker, you make the sound louder. Teachers might ask students to lower their volume when the classroom gets too noisy. Musicians adjust the volume of their instruments to blend properly in a performance.