In phonetics, rhotic consonants, also called tremulants or "R-like" sounds, are liquid consonants that are traditionally represented orthographically by symbols derived from the Greek letter rho, including ⟨R⟩, ⟨r⟩ from the Latin script and ⟨Р⟩, ⟨p⟩ from the Cyrillic script. They are transcribed in the International Phonetic Alphabet by upper- or lower-case variants of Roman ⟨R⟩, ⟨r⟩: r, ɾ, ɹ, ɻ, ʀ, ʁ, ɽ, and ɺ.
This class of sounds is difficult to characterise phonetically; from a phonetic standpoint, there is no single articulatory correlate common to rhotic consonants. Rhotics have instead been found to carry out similar phonological functions or to have certain similar phonological features across different languages. Although some have been found to share certain acoustic peculiarities, such as a lowered third formant, further study has revealed that this does not hold true across different languages. For example, the acoustic quality of lowered third formants pertains almost exclusively to American varieties of English. Being "R-like" is an elusive and ambiguous concept phonetically and the same sounds that function as rhotics in some systems may pattern with fricatives, semivowels or even stops in others—for example, "tt" in American English "better" is often pronounced as an alveolar tap, a rhotic consonant in many other languages.
The most typical rhotic sounds found in the world's languages are the following:
- Trill (popularly known as rolled r): The airstream is interrupted several times as one of the organs of speech (usually the tip of the tongue or the uvula) vibrates, closing and opening the air passage. If a trill is made with the tip of the tongue against the upper gum, it is called an apical (tongue-tip) alveolar trill; the IPA symbol for this sound is [r]. Most non-alveolar trills, such as the bilabial one, however, are not considered a rhotic.
- Many languages, such as Bulgarian, Swedish, Norwegian, Frisian, Italian, Spanish, Russian, Polish, Ukrainian, Dutch and most Occitan variants, use trilled rhotics. In the English-speaking world, the stereotyped Scottish rolled [r] is well known. The "stage pronunciation" of German specifies the alveolar trill for clarity. Rare kinds of trills include Czech ⟨ř⟩ [r̝] (fricative trill) and Welsh ⟨rh⟩ [r̥] (voiceless trill).
- Tap or flap (these terms describe very similar articulations): Similar to a trill, but involving just one brief interruption of airflow. In many languages taps are used as reduced variants of trills, especially in fast speech. However, in Spanish, for example, taps and trills contrast, as in pero /ˈpeɾo/ ("but") versus perro /ˈpero/ ("dog"). Also flaps are used as basic rhotics in Japanese and Korean languages, although frequently varying between a central flap [ɾ] and a lateral flap [ɺ].[further explanation needed] In some English dialects, such as American and Australian, flaps do not function as rhotics but are realizations of intervocalic apical stops (/t/ and /d/, as in rider and butter). The IPA symbol for this sound is [ɾ].
- Alveolar or retroflex approximant (as in most accents of English—with minute differences): The front part of the tongue approaches the upper gum, or the tongue-tip is curled back towards the roof of the mouth ("retroflexion"). No or little friction can be heard, and there is no momentary closure of the vocal tract. The IPA symbol for the alveolar approximant is [ɹ] and the symbol for the retroflex approximant is [ɻ]. There is a distinction between an unrounded retroflex approximant and a rounded variety that probably could have been found in Anglo-Saxon and even to this day in some[which?] dialects of English, where the orthographic key is r for the unrounded version and usually wr for the rounded version (these dialects will make a differentiation between right and write). Also used as a rhotic in some dialects of Armenian, Dutch, German, Brazilian Portuguese (depending on phonotactics) and Swedish.
- Uvular (popularly called guttural r): The back of the tongue approaches the soft palate or the uvula. The standard ars in Portuguese, French, German, Hebrew, and Danish are variants of this rhotic. If fricative, the sound is often impressionistically described as harsh or grating. This includes the voiced uvular fricative, voiceless uvular fricative, and uvular trill. In northern England, there were accents that once employed a uvular R, which was called a "burr".
- developmental non-rhotic ars: Many non-rhotic British speakers have a labialization to [ʋ] of their ars, which is between idosyncratic and dialectal (southern and southwestern England), and since it includes some RP speakers, somewhat prestigious. Apart from English, in all Brazilian Portuguese dialects the ⟨rr⟩ phoneme, or /ʁ/, may be actually realized as other, traditionally non-rhotic, fricatives (and most often is so), unless it occurs single between vowels, being so realized as a dental, alveolar, postalveolar or retroflex flap. In the syllable coda, it varies individually as a fricative, a flap or an approximant, though fricatives are ubiquitous in the Northern and Northeastern regions and all states of Southeastern Brazil but São Paulo and surrounding areas. The total inventory of /ʁ/ allophones is rather long, or up to [r ɻ̝̊ ç x ɣ χ ʁ ʀ ħ h ɦ], the latter eight being particularly common, while none of them except archaic [r], that contrast with the flap in all positions, may occur alone in a given dialect. Few dialects, such as sulista and fluminense, give preference to voiced allophones; elsewhere, they are common only as coda, before voiced consonants. Additionally, some other languages and variants, such as Haitian Creole and Timorese Portuguese use velar and glottal fricatives instead of traditional rhotics, too. In Vietnamese, depending on dialect, the rhotic can occur as [z], [ʐ] or [ʒ].
In broad transcription rhotics are usually symbolised as /r/ unless there are two or more types of rhotic in the same language; for example, most Australian Aboriginal languages, which contrast approximant [ɻ] and trill [r], use the symbols r and rr respectively. The IPA has a full set of different symbols which can be used whenever more phonetic precision is required: an r rotated 180° [ɹ] for the alveolar approximant, a small capital R [ʀ] for the uvular trill, and a flipped small capital R [ʁ] for the voiced uvular fricative or approximant.
The fact that the sounds conventionally classified as "rhotics" vary greatly in both place and manner in terms of articulation, and also in their acoustic characteristics, has led several linguists to investigate what, if anything, they have in common that justifies grouping them together. One suggestion that has been made is that each member of the class of rhotics shares certain properties with other members of the class, but not necessarily the same properties with all; in this case, rhotics have a "family resemblance" with each other rather than a strict set of shared properties. Another suggestion is that rhotics are defined by their behaviour on the sonority hierarchy, namely, that a rhotic is any sound that patterns as being more sonorous than a lateral consonant but less sonorous than a vowel. The potential for variation within the class of rhotics makes them a popular area for research in sociolinguistics.
See also 
- Ladefoged and Maddieson, p. 215
- Lindau, Mona (1978). "Vowel features". Language 54 (3): 541–63. doi:10.2307/412786. JSTOR 412786.
- Wiese, Richard (2001). "The phonology of /r/". In T Alan Hall. Distinctive Feature Theory. Berlin: Mouton de Gruyter. ISBN 3-11-017033-7.
- Ladefoged, Peter; Ian Maddieson (1996). "Rhotics". The Sounds of the World's Languages. Oxford: Blackwell. pp. 215–245. ISBN 0-631-19814-8.
- Barbosa & Albano (2004:5–6)
- Scobbie, James (2006). "(R) as a variable". In Roger Brown. Encyclopaedia of Language and Linguistics (2nd ed.). Oxford: Elsevier. pp. 337–344. ISBN 978-0-08-044299-0.