The Liu Shu categories are:
(1)pictographs (hsiang hsing);
(2)ideographs (chih shih);
(3)compound ideographs (hui i);
(4)compounds with both phonetic and meaning elements (hsing sheng);
(5)characters which are assigned a new written form to better reflect a changed pronunciation (chuan chu); and
(6)characters used to represent a homophone or near-homophone that are unrelated in meaning to the new word they represent (chia chieh).