The three states of matter are solid, liquid, and gas. Solids have a definite shape and volume, with particles closely packed in a fixed arrangement, making them incompressible. Liquids have a definite volume but take the shape of their container, with particles that are less tightly packed and able to flow past one another. Gases, on the other hand, have neither a definite shape nor a definite volume; their particles are widely spaced and move freely. There is also a fourth state, plasma, which occurs at extremely high temperatures and includes ionized gases like those found in stars.