onset (n.) (O)

A term used in PHONETICS and PHONOLOGY to refer to the initial functional element in a linguistic UNIT. The notion has been especially used in relation to the description of SYLLABLE structure, but it is also sometimes found in other contexts, such as in relation to INTONATION or RHYTHM units. A distinction is sometimes drawn between ‘simple’ syllabic onsets (containing only one segment) and ‘complex’ onsets (containing more than one segment). The maximal onset principle (or ‘CV rule’) states that a . . . VCV . . . string is universally syllabified as . . . V.CV. . . . In MORAIC phonology, onsets are thought not to contribute to syllable weight (unlike RHYMES – the notion of ‘onset/rhyme assymetry’). In OPTIMALITY THEORY, the onset constraint requires that all syllables begin with a consonant.

In PHONETICS, a term used in the ARTICULATORY description of SEGMENTS, referring to a phase (the onset phase) at the beginning of a segment during which the VOCAL ORGANS are approaching the maximal degree of CONSTRICTION (the ‘medial phase’). Onset phase specifically contrasts with offset phase, which shows the movement of the vocal organs towards the medial phase of the next segment.