In phonetics, contour describes speech sounds that behave as single segments but make an internal transition from one quality, place, or manner to another.
They are transcribed with series of either diacritics or tone letters, which with proper font support fuse into an iconic shape: [ma˨˩˦].
They are vowels that glide from one place of articulation to another, as in English boy and bow.
The most common contour consonants are by far the affricates[citation needed], such as English ch and j.
Other types of transition are attested in consonants, such as prenasalized stops in many African languages and nasal release in Slavic languages, the retroflex trill [ɽr] of Toda, the trilled affricate [ʈ͡r] of Fijian, voicing contours [d͡tʰ], [ɡ͡k͡xʼ] in ǃXóõ,[1] and even click contours (airstream contours) in Khoisan languages such as Nǁng, which start with a lingual (velaric) airstream mechanism and release with either a pulmonic mechanism (linguo-pulmonic clicks such as [ǃ͡q], [ǂ͡χ]) or an ejective mechanism (linguo-glottalic clicks such as [ǃʼ], [ǂ͡χʼ]).