Wackernagel's law

In morphology and syntax, a clitic (/ˈklɪtᵻk/ 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". A clitic 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 in "it's" for "it has" or "it is").

Clitics fall into various categories depending on their position in relation to the word to which they are connected.

A proclitic appears before its host. It is common in Romance languages. For example, in French, there is "il s'est réveillé" ("he woke up"), or "je t'aime" ("I love you").

An enclitic appears after its host.

A mesoclitic appears between the stem of the host and other affixes. For example, in Portuguese, conquistar-se-á "it will be conquered", dá-lo-ei "I will give it", matá-la-ia "he/she/it would kill her". These are found much more often in writing than in speech. It is even possible to use two pronouns inside the verb, as in dar-no-lo-á "he/she/it will give it to us", or dar-ta-ei (ta = te + a) "I will give it/her to you". As in other Romance languages, the Portuguese synthetic future tense comes from the merging of the infinitive and the corresponding finite forms of the verb haver (< Latin habere), which explains the possibility of separating it from the infinitive.

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