Within superspace representation, aperiodic crystals can be obtained by taking a section of a periodic crystal of higher dimension (up to 6D) and cutting at an irrational angle. While phonons change the position of atoms relative to the crystal structure in space, phasons change the position of atoms relative to the quasicrystal structure and the cut-through superspace that defines it. Therefore, phonon modes are excitations of the "in-plane" real (also called parallel or external) space, whereas phasons are excitations of the perpendicular (also called internal) space.