def get_motif_names():
    """
  Get common motif names.

  Get the names of some common motifs as strings.

  Returns
  -------
  motif_names : list
    A list of names (strings) of common motifs.
  """
    motif_names = ['Ms', 'Md']
    for i in range(1, 14):
        motif_name = 'M' + str(i)
        motif_names = motif_names + [motif_name]
    motif_names = motif_names + ['Mcoll'] + ['Mexpa']
    return motif_names
