Solid

as distinguished from liquids and gases, one of the three states of matter. A solid tends to retain its shape. A piece of wood, iron, or stone, however small, is a solid. Under the influence of heat and chemical action, all known solids may be changed into liquids and gases. Under pressure and the withdrawal of heat, most if not all gases have been reduced to liquids and solids. Freshly made putty, butter, and cheese are soft solids, while steel and granite are hard solids. See Hardness; for geometrical solids, see CUBE; CONE; SPHERE, etc.