syncope, apocope, aphesis

Syncope: loss of unstressed schwa in rapid tempos.
cf. s(up)posed, pos(i)tive, comf(or)table, yes(ter)day.
even in slow tempos, obligatory in bus(i)ness, ev(e)ning.

Apocope: loss of a word-final unstressed vowel ever' (= every), evnin' (=evening)

Aphesis: loss of a word-initial unstressed syllable
'way
'round
'bout
'scuse me
'cause
'pear
'fraid
'fits ok
'kay
'cept