Contour

In phonetics, contour describes speech sounds which behave as single segments, but which make an internal transition from one quality, place, or manner to another. These sounds may be tones, vowels, or consonants.

Many tone languages have contour tones, which move from one level to another. For example, Mandarin Chinese has four lexical tones. The high tone is level, without contour; the falling tone is a contour from high pitch to low; the rising tone a contour from mid pitch to high, and, when spoken in isolation, the low tone takes on a dipping contour, mid to low and then to high pitch. These are transcribed with series of either diacritics or tone letters, which with proper font support fuse into an iconic shape: [ma˨˩˦].

In the case of vowels, the word diphthong is used instead of 'contour'. These are vowels that glide from one place of articulation to another, as in English boy and bow. These are officially transcribed with a non-syllabic sign under one of the vowel letters: [bɔɪ̯], [baʊ̯], though when there is no chance of confusion, the diacritic is often left off for simplicity.

The most common contour consonants by far are the affricates, such as English ch and j. These start out as one manner, a plosive, and release into a different manner, a fricative, but behave as single consonants: [t͡ʃ], [d͡ʒ]. 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 [ɽ͡r] of Toda, the trilled affricate [t̪͡ʙ̥] of Wari’, voicing contours [d͡tʰ], [ɡ͡k͡xʼ] in ǃXóõ, and even click-plosive contours (airstream contours) in Khoisan languages such as Nǀuu, which start with a velaric airstream mechanism, and release with a pulmonic mechanism: [ǃ͡q], [ǂ͡χ].