In English there are certain words which have two forms of pronunciation: strong and weak (full and reduced) forms. These words include form-words and the following pronouns: personal, possessive, reflexive, relative and the indefinite pronoun 'some', denoting indefinite quantity.
These words have strong forms when they are stressed. Each of
these words usually has more than one weak form used in unstressed positions. There are three degrees of the reduction of strong forms:
1. The first degree consists in reducing the length of a vowel without changing its quality (the so-called quantitative reduction).
| Strong forms | Weak forms with quantitative reduction |
| for [f ɔ:] you [ju:] he [hi:] her [hε:] your [jɔ:] | for [f ɔ] you [ju] he [hi] her [hə] your [jɔ] |
2. The second degree of reduction consists in changing the quality of a vowel (the so-called qualitative reduction).
| Strong forms | Weak forms with qualitative reduction |
| for [f ɔ:] her [hε:] he [hi:] at [æt] can [kæn] was [wɔz] but [bʌt] | for [fə] her [hə] he [hə] at [tə] can [kn] was [wəz] but [bət] |
Most vowels in weak forms are reduced to the neutral [ə], although the long vowels [i:] and [u:] are usually reduced to [ı] and [u] respectively.
3. The third degree of reduction consists in the omission of a
vowel or consonant sound (the so-called zero reduction).
| Strong forms | Weak forms | |
| the vowels are omitted | am [æm] from [frɔm] of [ɔv] can [kæn] do[du:] is [ıs] shall [ʃæl] us [ʌs] must [mʌst] | [m] [frm] [v] [kn] [d] [s], [z] [ʃl] [s] [mst] |
| the consonants are omitted | he [hi:] him [hım] his [hız] must [mʌst] had [hæd] has [hæz] have [hæv] | [i], [ı] [ım] [ız] [məs] [əd] [əz] [əv] |
| both the vowels and consonants are omitted | and [ænd] has [hæz] have [hæv] had [hæd] will [wıl] shall [ʃæl] would [wud] | [n] [z], [s] [v] [d] [l] [l] [d] |