In semiconductor terminology, a hole is an energy deficit in a crystalline lattice due to (1) electrons ejected from unsatisfied covalent bonds at sites where an atom is missing, i.e., a vacancy, or (2) electrons supplied by atoms of impurities in the crystal, e.g., arsenic or boron. The free electrons from these sources move through the crystal, leaving positively charged energy deficits that are considered to move as they become alternately filled and vacated by electrons, creating a flow of positive electricity.See Semiconductor.