The smallest functioning unit in the composition of words, and the minimal distinctive unit of grammar. Morphemes are commonly classified into free forms (morphemes which can occur as separate words) adn bound forms (morphemes which cannot so occur - mainly affixes). A further distinction may be made between lexical and grammatical morphemes; the former are morphemes used for the construction of new words in a language; the latter are morphemes used to express grammatical relationships between a word and its context. [Crystal 2008: 300]