Other suprasegmental units

In addition to the syllable, research has provided evidence for a number of other prosodic units. First, the syllable itself may have structure – the initial cluster of consonants form an onset constituent, the final cluster of consonants form a coda constituent, the vowel or vowels which form the heart of the syllable are the nucleus; the nucleus and coda together may constitute a rhyme constituent. Another prosodic unit related to the expression of syllabicity, length, syllable-weight, and tone-bearingness is the mora. Groups of syllables may themselves be organized into a higher-level unit relevant to rhythm and stress, known as the foot, and finally there may be a panoply of word- and phrase-level constituents such as the prosodic word, phonological phrase, and intonational phrase. Such matters are part of the ongoing research program of phonological theory.