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.
[1] For some authors, only the term resonant is used with this broader meaning, while sonorant is restricted to the consonantal subset—that is, nasals and liquids only, not vocoids (vowels and semivowels).
Among consonants pronounced in the back of 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.
[citation needed] Voiceless sonorants are most common around the Pacific Ocean (in Oceania, East Asia, and North and South America) and in certain language families (such as Austronesian, Sino-Tibetan, Na-Dene and Eskimo–Aleut).
Hence, many English words from Ancient Greek roots have rh initially and rrh medially: rhetoric, diarrhea.