Latvian spelling has almost perfect correspondence between graphemes and phonemes. Note that simple vowel graphemes never represent diphthongs like in English. A sequence of graphemes representing a phoneme is called a polygraph. In some languages, due to monophthongization, graphemes that originally represented diphthongs now represent monophthongs. The 1995 revision considers only graphemes and disregards phonemic differences. The abugida nature of Bengali consonant graphemes is not consistent, however. A digraph is a case of polygraphy consisting of two graphemes. "Eunoia" is the shortest English word containing all five main vowel graphemes. Certain combinations of graphemes trigger special ligatures. Angle Brackets represent the graphemes, or orthographic letters, used to write a word. Syllabic laterals and trills are represented with duplication of the ordinary lateral and trill graphemes. Chinese typefaces often contain many variants of some graphemes. Languages with more graphemes can more readily exploit this. The interchangeability of the graphemes "i" and "y" is cancelled. The study of graphemes is called graphemics.