What is "clitic"

n. (context linguistics English) A morpheme that functions like a word, but never appears as an independent word, instead being always attached to a following or preceding word (or, in some cases, within a surrounding word).

In morphology and syntax, a clitic ( from Greek κλιτικός klitikos, "inflexional") is a morpheme that has syntactic characteristics of a word, but depends phonologically on another word or phrase. In this sense, it is syntactically independent but phonologically dependent, always attached to a host. The term is derived from the Greek for "leaning". It is pronounced like an affix, but plays a syntactic role at the phrase level. In other words, clitics have the form of affixes, but the distribution of function words. For example, the contracted forms of the auxiliary verbs in I'm and we've are clitics.

Clitics can belong to any grammatical category, although they are commonly pronouns, determiners, or adpositions. Note that orthography is not always a good guide for distinguishing clitics from affixes: clitics may be written as separate words, but sometimes they are joined to the word on which they depend (like the Latin clitic -que, meaning "and"), or separated by special characters such as hyphens or apostrophes (like the English clitic ’s). The word "clitic" is often used loosely for what may be better described as an affix or word.