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Mora (plural moras or morae) is a unit in phonology that determines syllable weight, which in some languages determines stress or timing. As with many technical linguistic terms, the definition of a mora varies. Perhaps the most succinct working definition was provided by the American linguist James D. McCawley in 1968: a mora is “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.

A syllable containing one mora is said to be monomoraic; a syllable with two moras is said to be bimoraic. Also, in rarer cases, a syllable with three moras is said to be trimoraic.http://en.wikipedia.org/wiki/Mora_(linguistics)