In grammar, a morpheme whose function is to indicate the formal or semantic class to which items belong are sometimes called classifiers, e.g. -ly is an adverb classifier, -ess is a 'femininity' classifier. The marking of lexical items as belonging to the same semantic class is an important feature in many languages (e.g. Chinese, Vietnamese, Hopi), and sometimes quite unexpected bases of classification are found, in terms of shape, size, colour, movability, animacy, status and so on. [Crystal 2003: 74]