The following 20 vowel phonemes are distinguished in BBC English (RP): [i :, a :, o :, u :, ç :, i, e, ?, ?, ?, ë (òèïó êðèøêà áóäèíî÷êà), ?; ei, ai, oi, à?, e?, ??, i?].
Principles of classification provide the basis for the establishment of the following distinctive oppositions:
1. Stability of articulation
1.1. monophthongs vs. diphthongs
bit - bait, kit - kite, John - join, debt - doubt
1.2. diphthongs vs. diphthongoids
bile - bee, boat - boot, raid - rude
2. Position of the tongue
2.1. horizontal movement of the tongue
a) front vs. central
cab - curb, bed - bird
b) back vs. central
pull - pearl, cart - curl, call - curl
2.2. vertical movement of the tongue
a) close (high) vs. mid-open (mid)
bid - bird, week - work
b) open (low) vs. mid-open (mid)
lark - lurk, call - curl, bard-bird
3. Position of the lips rounded vs. unrounded don - darn, pot - part
The English diphthongs are, like the affricates, the object of a sharp phonological controversy, whose essence is the same as in the case of affricates are the English diphthongs biphonemic sound complexes or composite monophonemic entities?
Diphthongs are defined differently by different authors. One definition is based on the ability of a vowel to form a syllable. Since in a diphthong only one element serves as a syllabic nucleus, a diphthong is a single sound. Another definition of a diphthong as a single sound is based on the instability of the second element. The 3d group of scientists defines a diphthong from the accentual point of view: since only one element is accented and the other is unaccented, a diphthong is a single sound.
D. Jones defines diphthongs as unisyllabic gliding sounds in the articulation of which the organs of speech start from one position and then glide to another position.
N.S. Trubetzkoy states that a diphthong should be (a) unisyllabic, that is the parts of a diphthong can not belong to two syllables; (B) monophonemic with gliding articulation; (C) its length should not exceed the length of a single phoneme.
In accordance with the principle of structural simplicity and economy American descriptivists liquidated the diphthongs in English as unit phonemes.
The same phonological criteria may be used for justifying the monophonemic treatment of the English diphthongs as those applicable to the English affricates. They are the criteria of articulatory, morphophonological (and, in the case of diphthongs, also syllabic) indivisibility, commutability and duration. Applied to the English diphthongs, all these criteria support the view of their monophonemic status.
Problem of length. There are long vowel phonemes in English and short. However, the length of the vowels is not the only distinctive feature of minimal pairs like Pete -pit, beet - bit, etc. In other words the difference between i: i. u: - ? is not only quantitative but also qualitative, which is conditioned by different positions of the bulk of the tongue. For example, in words bead- bid not only the length of the vowels is different but in the [i:] articulation the bulk of the tongue occupies more front and high position then in the articulation of [i].
Qualitative difference is the main relevant feature that serves to differentiate long and short vowel phonemes because quantitative characteristics of long vowels depend on the position they occupy in a word:
(A) they are the longest in the terminal position: bee, bar, her;
(B) they are shorter before voiced consonants: bead, hard, cord;
(C) they are the shortest before voiceless consonants: beet, cart.
Aspects and units of phonetics | Branches of phonetics | Methods of phonetic analysis | Spoken and Written language | Articulatory classification of English consonants | The articulatory classification of English Vowels | Definition of the phoneme and its functions. | Types of allophones and the main features of the phoneme | Methods of the phonemic analysis | Main phonological schools |