Elision

Elision: In speech and writing, the omission or slurring (eliding) of one or more vowels, consonants, or syllables, as in ol’ man old man, gonna going to, wannabe want to be, and the usual pronunciation of parliament (‘parlement’). Although in speech there is no direct indication of elision, in writing it is often marked by an apostrophe: didn’t did not, I’d’ve I would have. Elision is common in everyday speech and may specially marked in verse to ensure that readers keep the meter, and in th’empire. Foreign students often have trouble coming to terms with elisions created by the stress-time rhythm of English, which may make word sequences sound nonsensical, It is no good at all sounding like Snow good a tall.

Excerpted from: McArthur, Tom. The Oxford Concise Companion to the English Language. New York: Oxford University Press, 2005.