2.3. The vowel system of English

Substitution, or commutation, gives us a useful tool for establishing contrastive units, phonemes. The basic method of establishing a phoneme inventory, as we have shown for the consonant system of English, is finding a minimal pair of words which form contrast in one segment only, like hot, cot. Similarly, in word sets like heed, hid, head, had, etc., any two words can form a minimal pair in which there is contrast in respect of one vowel segment only.

There are 20 vowel sounds which have a distinctive function in Standard British English called RP or BBC English. (We specify it because other varieties, such as General American or Standard Scottish English have less, 15 or l6unitsonly.) For example, we can list the following words which can illustrate the contrasts established by replacing one vowel for the other in the phonologically identical structure. This will give us 17 vowel phonemes:

[bi:d] bead [bAd] bud

[bid] bid [Ш] bird

[bed] bed [beid] bayed

[baed] bad [baid] bide

[bcr.d] bard [boid] buoyed

[bud] bod [baud] bowed

[bo:d] board [bisd] £еа/г?

[bu:d] booed [be9d] Z>ara/

The missing three contrastive vowel units can be established by the opposition offool —full/u/, except— accept /a/', pair — poor /иэ/'.

Now we have to answer the question: Which features distinguish the vowel sounds in the minimal pairs, and through that distinction, differen­tiate the words or their grammatical forms, as in see — saw [si: - so:], man — men [maen - men], win — won [win - wAn]?

The basic classifying features of English vowels are quality, length, position of the lips, among which quality is the only phonemic one as a change in quality creates contrast and serves to distinguish words and their forms. Let us look at them in more detail:

1. Vowel quality which depends on the height and the front-back position

of the tongue; according to the vertical position of the tongue, vowels can be high (close), low (open) or mid-high (mid-open) and mid-low; according to the horizontal position of the tongue, they are classified into front, back and central.

2. Stability of articulation provides for a relatively homogeneous vowel quality throughout its production in case of a monophthong; a change in quality results in a diphthong; however, most of the long vowels are in between, and they are called diphthongoids.

3. Vowel length gives us two groups of vowel sounds, long and short, which are distinct in a number of features, such as

4. Tenseness: long vowels, including diphthongs, are tense, short vowels are lax,

5. Energy discharge: long vowels are unchecked (free), and short vowels are checked, i.e. produced with accompanying glottal activity, involving a rapid energy discharge in a short time interval,

6. Position of lips may distinguish rounded and unrounded vowels.

7. Position of the soft palate: all English vowels are oral; other languages, like French, for example, may have nasal vowels; English vowels may be nasalized before a nasal consonant but the nasal quality change is not phonemic as it is not contrastive, it is allophonic.

All the 20 vowel phonemes can be distinguished by quality alone, and that makes this feature phonemic.

Thus the 20 RP English vowels are grouped in the following way: twelve monophthongs (seven short vowels and five long ones) and eight diphthongs:

Short vowels	Long vowels	Diphthongs
i	i:	ei
e	a:	ai
se	з:	01
л	о:	ao
t)	u:	90
0		13
3		еэ из

The division into short and long vowels is important for the next highest phonological unit, the syllable: all long vowels, including diphthongs, maybe used in open syllables, while short vowels, with the exception of /э, i, u/, are checked and can be used in closed syllables only. Long vowels, including diphthongs, may form a long (heavy, or strong) syllable, and attract stress in a word, while short vowels are more likely to appear in short (light, or weak), and therefore unstressed syllables.