A centring diphthong is a diphthong that exists in non-rhotic accents. In phonetics, a diphthong (Greek δίφθογγος, diphthongos, literally with two sounds) is a vowel combination usually involving a quick but smooth movement from one vowel to another, often interpreted by listeners as a single vowel sound or phoneme. ... English pronunciation is divided into two main accent groups, the rhotic and the non-rhotic, depending on when the letter r (equivalent to Greek rho) is pronounced. ...
The centring diphthongs are:
/eə/ in hair
/ɪə/ in hear
/oə/ in more
/ʊə/ in poor
In Australian English, the centring diphthong /ɪə/ can become monophthongised to /ɪː/ especially when followed by a consonant. For the majority of speakers, /eə/ has already monophthongised to become /eː/, even when not followed by a consonant. Australian English is the form of the English language used in Australia. ...
Diphthongs in British English British English is a term primarily used by people outside of the UK to refer to the form of the English language spoken in the British Isles.
Diphthongs in Finnish Finnish is the language spoken by the majority of the population in Finland (92%) and by ethnic Finns outside Finland.
Diphthongs in German German (called Deutsch in German; in German the term germanisch is equivalent to English Germanic), is a member of the western group of Germanic languages and is one of the world's major languages.
There was also a possible 4th centringdiphthong /oə/ which appears to have been described for Australian English by McBurney (1887) (although we have no way of knowing whether words like "poor" [poə] were pronounced as one or two syllables and therefore as a diphthong or as two monophthongs).
Of the remaining two centringdiphthongs, only /ɪə/ (a) is common and (b) is produced as an in-gliding diphthong by a majority of Australian English speakers (but quite a large minority are now pronouncing it as [ɪː]).
The answer lies in the extent to which the centringdiphthongs can be accounted for by the features used in tables 1 and 2 if they undergo the process of monophthongisation.