Minor syllable

Primarily in Austroasiatic languages, in a typical word, a minor syllable, presyllable, or sesquisyllable, is a reduced syllable followed by a full tonic or stressed syllable. The minor syllable may be of the form or, with a reduced vowel, as in colloquial Khmer, or of the form with no vowel at all, as in Mlabri 'navel' and 'underneath', and Khasi 'rule', syrwet 'sign', 'transform', 'seed' and tyngkai 'conserve'.
This iambic pattern is sometimes called sesquisyllabic, a term coined by the American linguist James Matisoff in 1973. Although the term may be applied to any word with an iambic structure, it is more narrowly defined as a syllable with a consonant cluster whose phonetic realization is .

In historical linguistics

Sometimes minor syllables are introduced by language contact. Many Chamic languages as well as Burmese have developed minor syllables from contact with Mon-Khmer family. In Burmese, minor syllables have the form, with no consonant clusters allowed in the syllable onset, no syllable coda, and no tone.
Some reconstructions of Proto-Tai and Old Chinese also include sesquisyllabic roots with minor syllables, as transitional forms between fully disyllabic words and the monosyllabic words found in modern Tai languages and modern Chinese.