haven't

A contraction is a shortened version of the spoken and written forms of a word, syllable, or word group, created by omission of internal letters and sounds.
In linguistic analysis, contractions should not be confused with crasis, abbreviations and initialisms (including acronyms), with which they share some semantic and phonetic functions, though all three are connoted by the term "abbreviation" in layman’s terms. Contraction is also distinguished from morphological clipping, where beginnings and endings are omitted.
The definition overlaps with the term portmanteau (a linguistic blend), but a distinction can be made between a portmanteau and a contraction by noting that contractions are formed from words that would otherwise appear together in sequence, such as do and not, whereas a portmanteau word is formed by combining two or more existing words that all relate to a singular concept that the portmanteau describes.

View More On Wikipedia.org