Elision is the omission of one or more sounds
(such as a vowel, a consonant, or a whole syllable) in a word or phrase, producing a result that is easier for the speaker to pronounce.
Elision is normally unintentional, but it may be deliberate. The result may be impressionistically described as "slurred" or "muted."
An example of deliberate elision occurs in poetry as a stylistic device:
Excerpt from "The Rape of the Lock: Canto 1" by Alexander Pope
What dire offence from am'rous causes springs,
What mighty contests rise from trivial things,
I sing—This verse to Caryl, Muse! is due:
This, ev'n Belinda may vouchsafe to view:
Slight is the subject, but not so the praise,
If she inspire, and he approve my lays.
In the example above,
“amorous” is elided to
“am’rous” and
“even” is elided to
“ev'n”