Rhotic accents
Rhotic and non-rhotic are terms coined by the British phonetician John Wells (1982) for two kinds of spoken English as a fundamental contrastive feature. Received Pronunciation (RP) is a form of pronunciation of the English language, sometimes defined as the "educated spoken English of southeastern England". It is close to BBC English (the kind spoken by British newscasters) and it is represented in the pronunciation schemes of most British dictionaries. RP is rather a social accent and is not regional accent. It is associated, as a prestigious dialect, with the educated upper classes or with other people who have attended public schools for education in Britain.
Rhotic accent speakers pronounce a rhotic consonant -r in words like car, bar, far, hard, farm, and first. Non-rhotic speakers, for example, speakers of British English (BrE) and Australian English do not articulate the /r/ in all of such words.
That is, rhotic speakers articulate /r/ in all positions, while non-rhotic speakers pronounce /r/ only if it is followed by a vowel sound in the same phrase or prosodic unit as a "linking and intrusive r " in linguistic terms, non-rhotic accents are said to exclude the sound [r] from the syllable coda before a consonant or prosodic break.
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Bauman-Waengler, J. (2009). Introduction to phonetics and phonology: From concepts to transcription. Boston: Pearson. Gelderen. Retrieved from http://courses.nus.edu.sg/course/elltankw/history/Phon/D.htm