Chapter 1. Phonetics. Phonetics is a science of phoneme. Phoneme. Sound. Phonetic transcription. Allophone.

Speech is a complicated process and to study it requires a whole scientific subject –THE SCIENCE OF PHONETICS.
The science of phonetic laws of a language reflects its phonetic structure system of phonemes.
PHONETICS refers to the study of speech sounds.
THE PHONEME is the smallest unit of a language, which helps to differentiate vowels from consonants, one word from another, and one grammatical form from another of the same word.
E.g.: bead-бусина bid-велеть bed-постель  bad-плохой  bud-бутон
       [bi:d]            [bid]             [bed]              [bæd]           [bΛd ]
The English words are differentiated one from another by the vowel sounds.
E.g.: man – человек              men - люди
       [mæn]   - singal             [men] - plural
In this case, the vowel sounds differentiate two grammatical forms: singular and plural.
E.g.: Advise – советовать                                 advice – совет
               [z]                                                              [s]
The consonants [z] [s] differentiate noun and verb.
E.g.: Asks – Present            asked – Past
Here we see [s] [t] differentiate the grammatical forms: Past and Present Tenses.
Pronunciating «bed» instead of «bad» or vice versa, we may the hearer to be confused.
Now, we may conclude that all these different vowel sounds represent different phonemes.
SOUND is the minimum segment of the pronunciation of a word.
״this ״ has tree sounds [θ] [i] [s]
The method of representing each phoneme by one symbol is called PHONEMIC TRANSCRIPTION.
“Show” – the first sound is represented by the phonemic symbol [∫]. Each phoneme may be represented by different sounds in different positions, so the different [t]-sounds in tea and two both represent the [t] phoneme, and the three [h]-sounds in he, hat, who all represent the single [h] phoneme.
Phonemes can have several different physical forms or ALLOPHONES. Other word, the variant of a phoneme is allophone.
Allophones do not differentiate words or the grammatical forms of a word.
Eight – восемь                    eighth - восьмой
[eit]                                      [eitθ]
Consonants [t] are similar but slightly different.
[t] in eight is pronounced with the tip of the tongue pressed against the alveoli- it is an alveolar consonant.
[t] in eighth is pronounced with the blade of the tongue pressed against the upper teeth. It is a dental consonant.
There are the other components of the phonetic structure-syllable formation and syllable-stress and intonation.