clitic

morpheme with syntactic characteristics of a word but with phonological dependence on another word; e.g. ⟨-’m⟩ in ⟨I’m⟩ or ⟨-’ve⟩ in ⟨I’ve⟩; the possessive ⟨-’s⟩, the article ⟨a(n)⟩, and the infinitive marker ⟨to⟩ are sometimes considered clitics