(1) In phonology, a concept used to distinguish levels of syllabic prominence, based on the segmental constituency of syllables. Syllables can be metrically heavy (H) or light (L): a light (or ‘weak’) syllable is one whose rhyme comprises a short-vowel nucleus alone or followed by a coda of no more than one short consonant (in terms of phonological length, a mora); a heavy (or ‘strong’) syllable is any other type (its phonological length being greater than one mora). Syllables of structure CVVC or CVCC are sometimes referred to as ‘superheavy’. The notion of weight has also come to be important in several models of non-linear phonology.

(2) In syntax, a concept which relates the relative length/complexity of different elements of sentence structure. For example, a clause as subject or object would be considered heavier than a lexical noun phrase, which would be heavier than a pronoun. Such variations in length and complexity seem to influence the order of elements in languages: for example, there is a preference for short > long linearization in right-branching (VO) languages, and for long > short in left-branching (OV) languages.