A solid refers to one of three states of matter, characterized by having definite shape and volume. Atoms or molecules are packed closely together in an ordered arrangement.
The temperature at which a substance changes from its solid state to its liquid state. Each substance has its own unique melting point.
Crystal lattice: An ordered arrangement of atoms or molecules in three-dimensional space within solids. It gives solids their definite shape and structure.
Amorphous solid: A solid that lacks long-range order in the arrangement of its particles. Examples include glass and plastics.