The state of matter describes the physical form in which matter exists, primarily defined by the arrangement and movement of its constituent particles. The most commonly recognized states are solid, liquid, and gas, determined by the balance between kinetic energy and the forces of attraction between molecules. Solids exhibit a fixed shape and volume due to strong intermolecular forces, while liquids possess a fixed volume but take the shape of their container. Gases, conversely, have neither fixed shape nor volume because their particles are far apart and move randomly and rapidly. Beyond these common states, matter can also exist as plasma, an ionized gas, and under extreme conditions, as a supercritical fluid, which lacks a distinct boundary between liquid and gas phases. The transition between these states occurs when external energy is added or removed, altering the potential and kinetic energy of the system.