Which state of matter has a definite shape and volume?

The state of matter that has a definite shape and volume is solid. Solids have closely packed particles that are fixed in place, allowing them to maintain a specific shape and volume without needing a container. This contrasts with liquids, which take the shape of their container but maintain a constant volume, and gases, which do not have a definite shape or volume and can expand to fill their container. Plasma is an ionized state of matter where the particles are charged and move freely, also lacking a definite shape and volume. Therefore, the defining characteristics of solids uniquely qualify them as having both a definite shape and volume.