1. front / i: , e , eɪ , ᴂ , eə /

2. front-retracted / ɪ , ɪə /

3. central / ᴧ , ɜ: , ə , əʊ , aɪ , aʊ /

4. Back / ɒ , ᴐ: , u: , a: , ᴐɪ /

5. back-advanced / ʊ , ʊə /.

Front vowels are those which are produced with the bulk of the tongue in the front part of the mouth while the front of the tongue is raised in the direction of the hard palate, forming a large empty space in the back part of the mouth.

Front-retracted vowels are those which are produced with the bulk of the togue in the front part of the mouth, but somewhat retracted, while the front of the tongue is raides in the direction of the hard palate.

There are no front-retracted vowels in Russian.

Central vowels are those in which the central part of the tongue is raised towards the juncture between the hard and soft palate.

Back vowels are those which are produced with the bulk of the tongue in the back part of the mouth while the back of the tongue is raised in the direction of the soft palate, forming an empty space in the front part of the mouth.

Back-advanced vowels are those which are produced with the bulk of the tongue in the back part of the mouth, but somewhat advanced, while the back part of the tongue is raised in the direction of the front part of the soft palate.

There are no back-advanced vowels in Russian.

A slightly different approach seems to have been taken by British phoneticians. They do not single out the classes of front-retracted and back advanced vowels.

As for the Russian language, there are three (3) gradations, according to the horizontal movement of the tongue:

1. Front / и , э /

2. Central / ы , а /

3. Back / о, у /

The other articulatory characteristic of vowels as to the tongue position is its vertical movement. The way British and Soviet phoneticians approach this aspect is also slightly different. British scholars distinguish three (3) classes of vowels: high (or close), mid (or half-open), and low (or open) vowels. Soviet phoneticians made the classification more detailed distinguishing two subclasses in each class, i.e. broad and narrow variations of the three vertical positions of the tongue.

Thus the following six groups of vowels are distinguished:

close	narrow / i: , u: / broad / ɪ , ʊ , ɪə , ʊə /
mid	narrow / e , ɜ: , ə , eɪ , əʊ / broad / ə , ᴧ /
open	narrow / ᴐ: , eə , ᴐɪ , / broad / ᴂ , aɪ , aʊ, ɒ , a: /

In the Russian language they distinguish only three (3) gradations, according to the vertical movement of the tongue. They are:

1. Close / и , ы , у /

2. mid / э , о /

3. Open / а /.

Close (high) vowels are those which are produced when one of the parts of the tongue comes close to the roof of the mouth nd the air-passage is narrowed, but not so nuch as to form a consonant.

Open (low) vowels are those which are produced when the raised part of the tongue is very low in the mouth, and the air-passage is very wide.

Mid-open (mid) vowels are those which are produced when the raides part of the tongue is half way between its high and low positions.

The lip position

Traditionally three lip positions are distinguished, that is spread, neutral and rounded. But for the purpose of classification it is sufficient to distinguish between two lip positions: rounded and unrounded (neutral). Both in the English and Russian language exist labialized and non-labialized vowel phonemes. The difference is in the degree of roundness. In English lip rounding is not relevant phonologically since no two words can be differentiated on its basis. Lip rounding takes place rather due to physiological reasons than to any other. The degree of rounding is different and depends on the height of the raised part of the tongue; the higher it is raised the more rounded the lips are. So lip rounding is a phoneme constitutive indispensable feature, because no back vowel can exist without it.

The English rounded vowels are / ɒ , ᴐ: , ʊ , u: /. The English unrounded vowels are / ɪ , i: , e , ᴂ , a: , ɜ: , ə , ᴧ /.

The lips while producing rounded vowel sounds in the Russian language in comparison with the English ones are more protruded. The rounded phonemes in Russian are / o , y /; the unrounded vowel phonemes are / а , и , э , ы /.

Length

According to the length, vowels may be long and short. The following English vowels may be described as long: / i: , a: , ᴐ: , u: , ɜ: /. And these ones as short: / ɪ , e , ᴂ , ɒ , ʊ , ᴧ , ə /.

There is no differentiation of Russian vowel phonemes according to the length. Stressed vowels are longer than unstressed in the Russian language, but it does not influence on meaning.

The degree of tenseness

According to the degree of tenseness vowels are divided into tense and lax.

Tense vowels are produces when the organs of speech are tense: the muscles of the tongue, the walls of the mouth-resonator and of the pharynx are tense. all the English long vowels are tense / i: , a: , ᴐ: , u: , ɜ: /.

Lax vowels are those which are produced with lesser tenseness of the speech organs. All the English short vowels ale lax / ɪ , e , ᴂ , ɒ , ʊ , ᴧ , ə /.

The greater tenseness of long vowels is closely connected with their length. In pronouncing a long vowel the organs of speech are held in a certain position for a rather long time. Retaining the quality of a long vowel unchanged requires greater muscular tension of the organs of speech than in the articulation of a short vowel.

Russian vowel phonemes are not differentiated according to their tenseness, bur one and the same vowel is more tense in a stressed syllable than in an unstressed one. The phonological relevant position is missing.

The character of the end of the vowel phonemes

From this point of view they may be: checked and unchecked.

Checked vowels are those which are pronounced without any lessing the force of utterance towards their end. They have a strong end. They end abruptly and are interrupted by the consonant immediately following. Therefore they can only occur in a closed syllable, i.e. a syllable which ends in a consonant sound. The English short vowels under stress checked. So are the English long vowels and diphthongs when followed by voiceless consonants, e.g. bed /bed/, not /nɒt/, hat /hᴂt/.

Unchecked vowels are those which are pronounced with lessing the force of utterance towards their end. Therefore, they have a weak end.

The English long vowels and diphthongs when stressed both in open and in closed syllables followed by voiced consonants are unchecked. The same is true of all the English unstressed vowels no matter whether long or short, e.g. free /fri:/, card /ka:d/.

As for the Russian language all the vowels are unchecked.