Elision
In linguistics, an elision is the omission of one or more sounds (like a vowel, a consonant or a syllable) in a word or phrase. Elisions make a language easier to say, and faster--and in English, working hand-in-hand with the schwa sound, they make linking and connected speech possible.
Elisions can be clearly seen in what I call "official" contractions, like "isn't" (the contracted version of "is not,") "I'll" ("I will"), "haven't" ("have not"), etc. that we often see written in books or dialogue.
"Unofficial" contractions aren't generally seen in writing, so there aren't a lot of rules about how to write these elisions--or even when they should be said. They aren’t mandatory, and in formal writing, the words are written the same whether or not the speaker would elide them. When we speak rapidly, we use more elisions than when we are talking more slowly--or when we are trying to emphasize a thought or make a point.
As a result, listening to words in a conversation may seem entirely unrelated to seeing those same words in writing. The omission of certain sounds, or the conversion of sounds to the schwa sound may make it seem as though English speakers leave out entire words.
However, it is important to remember that every word is necessary in a sentence. So, even though the process of compressing words together might cause some sounds to be lost, all words must be said (in some form) if the message is to be completely communicated.
Here are a few examples of elisions, written more or less phonetically.
dunno= don’t know
fish`n’ chips= fish and chips (many times, "and" is spoken as a single "n" sound)
wanna= want to
gonna= going to
gotta = got to
lemme = let me
gimme= give me
wouldn’t’ve= would not have
ice tea= iced tea
kinduh= kind of
sickuh = sick of (very annoyed with something, fed up)
doyuh= Do you
‘cause= because
kamra= camera
‘em= them
uh= of (before words that start with a consonant)
oubou’chuh= about you