Concept
In English, many vowel shifts affect only vowels followed by /r/ in rhotic dialects, or vowels that were historically followed by /r/ that has been elided in non-rhotic dialects. Most of them involve the merging of vowel distinctions and so fewer vowel phonemes occur before /r/ than in other positions of a word. Rhoticity in English In rhotic dialects, /r/ is pronounced in most cases. In General American English (GA), /r/ is pronounced as an approximant ɹ or ɻ in most positions, but after some vowels, it is pronounced as r-coloring. In Scottish English, /r/ is traditionally pronounced as a flap ɾ or trill r, and there are no r-colored vowels. In non-rhotic dialects like Received Pronunciation (RP), historic /r/ is elided at the end of a syllable, and if the preceding vowel is stressed, it undergoes compensatory lengthening or breaking (diphthongization). Thus, words that historically had /r/ often have long vowels or centering diphthongs ending in a schwa /ə/, or a diphthong followed by a schwa. earth: GA [ɝθ], RP [ɜːθ] here: GA [ˈhɪɚ], RP [ˈhɪə] fire: GA [ˈfaɪɚ], RP [ˈfaɪə] In most English dialects, there are vowel shifts that affect only vowels before /r/ or vowels that were historically followed by /r/. Vowel shifts before historical /r/ fall into two categories: mergers and splits. Mergers are more common and so most English dialects have fewer vowel distinctions before historical /r/ than in other positions of a word. In many North American dialects, there are ten or eleven stressed monophthongs; only five or six vowel (rarely seven) contrasts are possible before a preconsonantal and word-final /r/ (beer, bear, burr, bar, bore, bor, boor). Often, more contrasts exist if /r/ appears between vowels of different syllables. In some American dialects and in most native English dialects outside North America, for example, mirror and nearer do not rhyme, and some or all of marry, merry, and Mary are pronounced distinctly. (In North America, those distinctions are most likely to occur in New York City, Philadelphia, some of Eastern New England (including Boston), and in conservative Southern accents.