The sonority hierarchy is a ranklist of speech sounds. Speech sounds are typically ranked according to their manner of articulation. Accordingly, in all sonority hierarchies, vowels are at the top of the hierarchy, consonants at the bottom. Most hierarchies are more finely graded, e.g., vowels > sonorant consonants > obstruents (Zec 1995), or vowels > glides > liquids > nasals > obstruents (Clements 1990), or vowels > liquids > nasals > voiced fricatives > voiceless fricatives = voiced plosives > voiceless plosives (Anderson & Ewen 1987). Some hierarchies assign each individual sound to a rank of its own, thus ranking sounds also according to their place of articulation (Ladefoged 1993).
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