When you hear the word abbreviation, you tend to think of something like FBI or UFO. And it’s true that both of those are abbreviations. But the term abbreviation is actually a much broader one than many people realise, encompassing any kind of shortening of a word. Let’s look at some of the different types:
initialism: an abbreviation formed by letters (usually representing the first letters of words in a phrase or the name of an organisation), in which the letters are pronounced separately, e.g. FBI, UFO, OMG, REM
acronym: formed by letters (usually representing the first letters of words in a phrase or the name of an organisation), and pronounced as a single word, e.g. NASA, NATO, laser, radar, lol (though some treat it as an initialism. Also, UFO, in some languages, is an acronym, and pronounced oofoh)
contraction: so common you might not think of it as an abbreviation – when two words are joined together to make one, usually with some letters removed and replaced by an apostrophe, e.g. don’t, can’t
elision: basically the same as a contraction, only in spoken English, e.g. I’m, let’s
abbreviation: while all the above are abbreviations, the term can also be used to refer to the simple shortening of a word by removing part of it, e.g. abbrv., Mr. Prof.
What about words like totes, or, and I feel dirty just typing this, totes emotes (totally emotional – sigh…) which are basically abbreviations, but also add an s? For the sake of expedience, they can still be referred to as abbreviations, though perhaps if we don’t give them a name, no-one will use them. That’d be totes OMG.