ABSTRACT
We have defined ferroic phase transitions as nondisruptive phase transitions involving a change of point-group symmetry. For transitions defined in this way a prototype symmetry can always be assigned or chosen. Ferroelectric phase transitions are a subset of ferroic transitions such that the ferroic phase belongs to one of the 10 polar classes, namely l , 2 ,3 ,4 ,6 , r a , rara2, 3?7i, 4771771, 6777-771.
