translation. If arbitrary translations were allowed, one could make a primitive cell half the size of the true one, and translate twice as often, as an example.

Another way of defining the size of a primitive cell that avoids invoking lattice translation operations, is to say that the primitive cell is the smallest possible component of a lattice (or crystal) that can be repeated to reproduce the whole lattice (or crystal), and that contains exactly one lattice point. In either definition, the primitive cell is characterized by its small