centre (n.)

The top part of the TONGUE, between FRONT and BACK, and used especially in the production of ‘central VOWELS’ (also called ‘neutral’ vowels), such as the  sound which opens the word asleep and closes the word sofa. In a sense, when compared with the theoretical extremes of vowel ARTICULATION which define the CARDINAL VOWELS in PHONETICS, all real LANGUAGE vowels are centralized; but the term is usually used to refer to cases where a vowel normally articulated in the periphery of the vowel area comes to be produced nearer the centre of the mouth, as when bacon and [= and] eggs becomes, in normal colloquial speech, bacon  eggs. Several degrees of this process of centralization can be heard. Markedly ‘centralized vowels’ are common in several urban British DIALECTS, for example. A DIPHTHONG which involves a GLIDE towards the centre of the mouth may be referred to as a ‘centring’ diphthong.

The most SONOROUS part of a SYLLABLE may be referred to as the ‘centre’ (or NUCLEUS), e.g. the [u:] in the word boot [bu:t].

In those types of grammatical PHRASE where several words depend on one HEAD word (ENDOCENTRIC constructions), the head is often referred to as the ‘centre’ of the phrase.