Rhotic consonant
Rhotic consonants, or "R"-like sounds, are non-lateral liquids. This class of sounds is difficult to characterise phonetically, though most of them share some acoustic peculiarities, most notably a lowered third formant in their sound spectrum. However, "being r-like" is a strangely elusive feature, and the very same sounds that function as rhotics in some systems may pattern with fricatives, semivowels or even stops in others. The most typical rhotic sounds found in the worlds 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, we speak of an apical (tongue-tip) alveolar trill, the IPA symbol for this sound is [r]. If it is made with the uvula against the back of the tongue, we speak of a uvular trill, the IPA symbol for this sound is [ʀ]. The bilabial trill, however, is not considered a rhotic.
- Tap or flap (these terms refer to very similar articulations): Not unlike 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. Note, however, that in Spanish, for example, taps and trills contrast, as in pero /ˈpeɾo/ ("but") versus perro /ˈpero/ ("dog"). In some English dialects (for example American, Australian) flaps do not function as rhotics but are realizations of intervocalic apical stops ([t] or [d], for example in rider or 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].
- Uvular or velar approximant or fricative: The back of the tongue approaches the soft palate or the uvula. The standard /r/'s in French, German, and Danish are variants of this type of rhotic. If fricative, the sound is often impressionistically described as harsh or grating. This includes the voiced uvular fricative, voiceless uvular fricative, voiced velar fricative, voiceless velar fricative, and the velar approximant.
In broad transcription rhotics are usually symbolised as /r/ unless there are two or more types of rhotic in the same language. The IPA has a full set of different symbols which can be used whenever more phonetic accuracy 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.