1. Monopthongs

2. Diphthongs

3. Diphthongoids.

A monophthong is a pure (unchanging) sound, that does not change its stability of articulation. In its pronunciation the organs of speech do not perceptibly change their position throughout the duration of the vowel. There are ten (10) monophthongs in English: / ɪ , e , ᴂ , a: , ɒ , ᴐ: , ʊ , ᴧ , ɜ: , ə /.

A diphthong is a complex sound that consists of two vowel elements pronounced so to form a single syllable. In pronunciation of a diphthong the organs of speech start in the position of one vowel and glide gradually in the position of another vowel, whose full formation is generally not accomplished. The first element of an English diphthong is called the nucleus. It is strong, clear and distinct. The second element, the glide, is rather weak. From the articulatory point of view, a diphthong is an indivisible phonetic whole. There are eight (8) diphthongs in English: / eɪ , aɪ , ᴐɪ ; aʊ , əʊ ; ɪə , eə , ʊə /.

The articulatory indivisibility of an English diphthong manifests itself also in its syllabic and morphological indivisibility, i.e. neither the point of syllabic division nor a morpheme boundary can separate the glide of an English diphthong from its nucleus, e.g. / ˈpeɪ - ɪŋ / (paying), / ˈflaɪ - ɪŋ / (flying).

A diphthongoid is a sound where the organs of speech change their position very slightly. There are only two (2) diphthongoids in English: / i: , u: /.

There is a phonological problem connected with the classification of vowels according to the principle of the stability of articulation: the phonemic status of the so-called "triphthongs", such as / aɪə , aʊə /, e.g. hire or higher, flour and flower. A true triphtong should be a monophonemic entity indivisible by the point of syllable division or a morpheme boundary. But the so-called triphthongs in English do not meet any of these requirements. The disyllabic nature of such sound complexes often manifests itself also in their morphophonogical divisibility, with morpheme boundary passing always between the glide / aɪə / or /aʊə / and the neutral vowel /ə/. Hire / haɪə /, which is morphological indivisible, and higher / haɪə /, which consists of two morphemes (high + er / haɪ +ə /), but sounds exactly like hire. On the basis of this evidence the so-called triphthongs / aɪə / and /aʊə / should be regarded as biphonemic vowel combinations consisting of a diphthong as a unit phoneme and the neural vowel phoneme / ə /.

In the Russian vocalic system there’s no such a subdivision. In the Russian language there are only six (6) pure monophthongs, that is / a , и, о, y , ы , э /.

The syllabic and morphological indivisibility of a diphthong as a unit phoneme is also proved by the fact that in those languages which have no true diphthongs but only biphonemic diphthong‒like sound complexes, such as Russian, the elements of such a sound complex are easily separated from each other by the point of syllable division and a morphene boundary, e. g. / чай ‒ ча-йу/ (чай ‒ чаю), /цэлый--цэлыйь/ (целый ‒ целые). These also illustrate the high degree of combinability of the elements of a diphthong ‒ like sound complex: any Russian vowel may be combined with /й/. The phoneme /й/ may also occur before any Russian vowel, except /ы/.

The position of the tongue

The position of the tongue in the mouth cavity is characterised from two aspects, that is the horizontal and vertical movement of the tongue.

According to the horizontal movement Soviet phoneticians distinguish five (5) classes of English vowels. They are: