The earliest traces of a loss of /r/ in English are found in the environment before /s/ in spellings from the mid-15th century: the Oxford English Dictionary reports bace for earlier barse (today "bass", the fish) in 1440 and passel for parcel in 1468. In the 1630s, the word juggernaut is first attested, which represents the Sanskrit word jagannāth, meaning "lord of the universe". The English spelling uses the digraph er to represent a Hindi sound close to the English schwa. Loss of coda /r/ apparently became widespread in southern England during the 18th century; John Walker uses the spelling ar to indicate the broad A of aunt in his 1775 dictionary and reports that card is pronounced "caad" in 1791 (Labov, Ash, and Boberg 2006: 47).
Non-rhotic speakers pronounce an [ɹ] in red, and most pronounce it in torrid and watery (in each case the [ɹ] is followed by a vowel) but not in hard, nor car or water. However, in most non-rhotic accents, if a word ending in written "r" is followed closely by another word beginning with a vowel, the [ɹ] is pronounced—as in water ice. This phenomenon is referred to as "linking R". Many non-rhotic speakers also insert epenthetic [ɹ]s between vowels when the first vowel is one that can occur before syllable-final r (drawring for drawing). This so-called "intrusive R" is frowned upon by those who use the non-rhotic Received Pronunciation but even they frequently "intrude" an epenthetic [ɹ] at word boundaries, especially where one or both vowels is schwa; for example the idea of it becomes the idea-r-of it, Australia and New Zealand becomes Australia-r-and New Zealand. The typical alternative used by RP speakers is to insert a glottal stop where an intrusive R would otherwise be placed.
For non-rhotic speakers, what was historically a vowel plus [ɹ] is now usually realized as a long vowel. So car, hard, fur, born are phonetically /kɑː/, /hɑːd/, /fɜː/, /bɔːn/. This length is retained in phrases, so car owner is /kɑːɹəʊnə/. But a final schwa remains short, so water is /wɔːtə/. The vowels /iː/ and /uː/ (or /ʊ/), when followed by r, become diphthongs ending in schwa, so near is /nɪə/ and poor is /pʊə/. The same happens to diphthongs followed by R (or they end in /ɚ/ in rhotic speech and that sound turns into a schwa as usual in non-rhotic speech): tire is /taɪə/ and sour is /saʊə/ (New Shorter Oxford English Dictionary). For some speakers some long vowels alternate with a diphthong ending in schwa, so wear is /wɛə/ but wearing is /wɛːɹiŋ/. Some pairs of words with distinct pronunciations in rhotic accents are homophones in many non-rhotic accents. Examples in Received Pronunciation include father and farther; draws and drawers; formally and formerly; area and airier. In Australian English, which has the weak vowel merger, pairs like batted/battered or boxes/boxers are homophones. Syllabication interacts with rhoticity: rhotic sheer and Shi'a respectively have one and two syllables; in some non-rhotic speech, this may be insufficient for distinguishing them.
Most speakers of North American English are rhotic. Outside North America, rhotic accents can be found in Barbados, Ireland and Scotland. In England, rhotic accents are found in the West Country, the Corby area, most of Lancashire, some western fringes of Yorkshire and in the areas that border Scotland. Most speakers of Indian English have a rhotic accent. Other areas with rhotic accents include Otago and Southland in the far south of New Zealand's South Island, where a Scottish influence is apparent.
In the United States, much of the South was once non-rhotic, but in recent decades non-rhotic speech has declined. Today, non-rhoticity in Southern American English is found primarily among older speakers, and only in some areas such as New Orleans (where it is known as the Yat accent), southern Alabama, Savannah, Georgia, and Norfolk, Virginia (Labov, Ash, and Boberg 2006: 47–48). Parts of New England, especially Boston, are non-rhotic as well as New York City and surrounding areas. The case of New York is especially interesting because of a classic study in sociolinguistics by William Labov showing that the non-rhotic accent is associated with older and middle- to lower-class speakers, and is being replaced by the rhotic accent. African American Vernacular English (AAVE) is largely non-rhotic.
There are a few accents of Southern American English where intervocalic [ɹ] is deleted before an unstressed syllable and at the end of a word even when the following word begins with a vowel. In such accents, pronunciations like [kæəlaːnə] for Carolina and [bɛːʌp] for "bear up" are heard (Harris 2006: 2–5). These pronunciations also occur in AAVE (Pollock et al. 1998)
Among the Turkic languages, Uyghur displays more or less the same feature, as syllable-final /r/ is dropped, while the preceding vowel is lengthened: for example Uyghurlar [ʔʊɪ'ʁʊːlaː] ‘Uyghurs’. The /r/ may, however, sometimes be pronounced in unusually "careful" or "pedantic" speech; in such cases, it is often mistakenly inserted after long vowels even when there is no phonemic /r/ there.
Similarly in Yaqui, an indigenous language of northern Mexico, intervocalic or syllable-final /r/ is often dropped with lengthening of the previous vowel: pariseo becomes /pa:ˡseo/, sewaro becomes /sewajo/.
In some dialects of Brazilian Portuguese, word-final /r/ is unpronounced or becomes simply an aspiration (mostly in the interior of Minas Gerais, São Paulo, Paraná and Mato Grosso do Sul states), while in Thai, pre-consonantal /r/ is unpronounced.