What are the three states of matter?

The three states of matter most commonly recognized in classical physics are solid, liquid, and gas. In the solid state, particles are tightly packed together in a fixed arrangement, which gives solids a definite shape and volume. In the liquid state, the particles are still close together but can move past one another, allowing liquids to take the shape of their container while maintaining a fixed volume. In the gas state, the particles are far apart and move freely, occupying whatever space is available, which results in no fixed shape or volume.

While other states of matter do exist—such as plasma, which consists of ionized gases, and vapor, which is often a gaseous form of a substance that is liquid at room temperature—they are not among the primary three states that we typically refer to in basic science education.