Matter comes in many forms. At this point, we will consider three: solid, liquid and gas. A solid has a definite shape and it takes up a fixed volume. On the other hand, liquid has a fixed volume, but no definite shape. A liquid will change its shape to fit its container. A gas has no definite shape and no fixed volume. Like a liquid, a gas will change its shape to fit its container, but it will also expand to fill the entire volume of the container.

Solid (s) – rigid, fixed volume, fixed shape.
Liquid (l) – definite volume, but no definite shape.
Gas (g) – no fixed shape, no fixed volume.