clitic

/ˈklɪ.tɪk/

IPA: /K L IH1 T IH0 K/

noun
  1. 1

    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).

Source: https://en.wiktionary.org/wiki/clitic