Syllable different from mora
Weight
A heavy syllable is generally one with a branching rime, i.e. it is either a closed syllable that ends in a consonant, or a syllable with a branching nucleus, i.e. a long vowel or diphthong. The name is a metaphor, based on the nucleus or coda having lines that branch in a tree diagram.
In some languages, heavy syllables include both VV (branching nucleus) and VC (branching rime) syllables, contrasted with V, which is a light syllable.
In other languages, only VV syllables are considered heavy, while both VC and V syllables are light.
Some languages distinguish a third type of superheavy syllable, which consists of VVC syllables (with both a branching nucleus and rime) or VCC syllables (with a coda consisting of two or more consonants) or both.
In moraic theory, heavy syllables are said to have two moras, while light syllables are said to have one and superheavy syllables are said to have three. Japanese phonology is generally described this way.
Many languages forbid superheavy syllables, while a significant number forbid any heavy syllable. Some languages strive for constant syllable weight; for example, in stressed, non-final syllables in Italian, short vowels co-occur with closed syllables while long vowels co-occur with open syllables, so that all such syllables are heavy (not light or superheavy).
The difference between heavy and light frequently determines which syllables receive stress – this is the case in Latin and Arabic, for example. The system of poetic meter in many classical languages, such as Classical Greek, Classical Latin, Old Tamil and Sanskrit, is based on syllable weight rather than stress (so-called quantitative rhythm or quantitative meter).