A mora (plural morae or moras; often symbolized μ) is a unit in phonology that determines syllable weight, which in some languages determines stress or timing. The definition of a mora varies. In 1968, American linguist James D. McCawley defined it as "something of which a long syllable consists of two and a short syllable consists of one". The term comes from the Latin word for "linger, delay", which was also used to translate the Greek word chronos (time) in its metrical sense.

Monomoraic syllables have one mora, bimoraic syllables have two, and trimoraic syllables have three, although this last type is relatively rare.