An abbreviation (from Latin brevis, meaning short) is a shortened form of a word or phrase. Usually, but not always, it consists of a letter or group of letters taken from the word or phrase. For example, the word abbreviation can itself be represented by the abbreviation abbr., abbrv. or abbrev.

In strict analysis, abbreviations should not be confused with contractions or acronyms (including initialisms), with which they share some semantic and phonetic functions, though all three are connoted by the term "abbreviation" in loose parlance.An abbreviation is a shortening by any method; a contraction is a reduction of size by the drawing together of the parts. A contraction of a word is made by omitting certain letters or syllables and bringing together the first and last letters or elements; an abbreviation may be made by omitting certain portions from the interior or by cutting off a part. A contraction is an abbreviation, but an abbreviation is not necessarily a contraction. However, normally, acronyms are regarded as a subgroup of abbreviations (e.g. by the Council of Science Editors). Abbreviations can also be used to give a different context to the word itself, such as "PIN Number" (wherein if the abbreviation were removed the context would be invalid).