Solid, one of the three basic states of matter, the others being liquid and gas. A solid forms from liquid or gas because the energy of atoms decreases when the atoms take up a relatively ordered, three-dimensional structure.
A solid, as opposed to a liquid or gas, has a size and shape to it. It doesn't flow like water or disappear into the air.
Unlike a gas or liquid, a solid has a fixed shape, and unlike a gas, a solid has a fixed volume. In most solids (with exceptions such as glass), the molecules are arranged in crystal lattices of various sizes.
A solid is a substance that stays the same shape whether it is in a container or not. Solids turn to liquids at certain temperatures. A substance that is solid is very hard or firm. The snow had melted, but the lake was still frozen solid. A solid object or mass does not have a space inside it, or holes or gaps in it.
The particles of a solid are very close together. It melts when it changes from the solid state to the liquid state. The same mass of liquid will have slightly greater volume than the solid. As ...