When crystals are stressed they may be deformed plastically by gliding or sliding along planes between rows of atoms within the crystal structure. This may take the form of ‘translation gliding’, whereby one or more rows of atoms may be displaced laterally along the glide plane, or ‘twin gliding’, where a smaller displacement is taken up by each row within the lattice. Twins produced in this way are called ‘gliding twins’ or ‘deformation twins’.