|Manners of articulation|
In phonetics and phonology, a sonorant or resonant is a speech sound that is produced with continuous, non-turbulent airflow in the vocal tract; these are the manners of articulation that are most often voiced in the world's languages. Vowels are sonorants, as are consonants like /m/ and /l/: approximants, nasals, flaps or taps, and most trills.
In older usage, the term resonant was a synonym for sonorant, and sonorant was a narrower term, referring to all resonants except vowels and semivowels.
Whereas obstruents are frequently voiceless, sonorants are almost always voiced. A typical sonorant consonant inventory found in many languages comprises the following: two nasals /m/, /n/, two semivowels /w/, /j/, and two liquids /l/, /r/.citation needed
In the sonority hierarchy, all sounds higher than fricatives are sonorants. They can therefore form the nucleus of a syllable in languages that place that distinction at that level of sonority; see Syllable for details.
Among consonants pronounced in the back in the mouth or in the throat, the distinction between an approximant and a voiced fricative is so blurred that no language is known to contrast them. Thus, uvular, pharyngeal, and glottal fricatives never contrast with approximants.
Voiceless resonants are rare; they occur as phonemes in only about 5 percent of the world's languages.1 Voiceless sonorants tend to be extremely quiet and very difficult to recognise even for those people whose language does contain them.
In every case where a voiceless sonorant does occur, there is a contrasting voiced sonorant (i.e. whenever a language contains a phoneme such as /r̥/, it also contains a corresponding voiced phoneme, /r/ in this case).citation needed
Voiceless sonorants are most common around the Pacific Ocean — in Oceania, East Asia, and North and South America — in certain language families, such as Austronesian, Sino-Tibetan, Na-Dene and Eskimo–Aleut.
Voiceless [r̥ l̥ ʍ], and possibly [m̥ n̥], are hypothesized to have occurred in various dialects of Ancient Greek. The Attic dialect of the Classical period likely had [r̥] as the regular allophone of /r/ at the beginning of words, and possibly when doubled inside words. Hence, many English words from Ancient Greek roots have rh initially and rrh medially: rhetoric, diarrhea.