text: The screw axis is noted by a number, n, where the angle of rotation is . The degree of translation is then added as a subscript showing how far along the axis the translation is, as a portion of the parallel lattice vector.  For example, 2 is a 180° (twofold) rotation followed by a translation of  of the lattice vector. 3 is a 120° (threefold) rotation followed by a translation of  of the lattice vector.
  The possible screw axes are: 2, 3, 3, 4, 4, 4, 6, 6, 6, 6, and 6.
  There are 4 enantiomorphic pairs of axes: (3 – 3), (4 – 4), (6 – 6), and (6 – 6). This enantiomorphism results in 11 pairs of enantiomorphic space groups, namely