The term 'A State of Matter' refers to the three main states of matter: GAS, SOLID, and liquid. GAS is a state of matter that has no fixed shape or volume and is composed of particles that are in constant motion. SOLID is a state of matter that has a fixed shape and volume and is composed of particles that are closely packed together. Liquid is a state of matter that has no fixed shape but does have a fixed volume and is composed of particles that are loosely packed together.