Crystalline Solid
A solid in which the constituent particles are arranged in a regular, repeating three-dimensional pattern extending over long distances.
Unit
Dimensionless
In depth
Long-range order gives crystalline solids sharp melting points, definite geometric external form, characteristic cleavage planes and anisotropic physical properties. They diffract X-rays into discrete spots, which is how their internal structures are determined.
Examples in the real world
Quartz, sodium chloride, diamond and metallic copper; snowflakes with their sixfold symmetry.