mora

The term "mora" in phonology refers to a rhythmic unit of sound length, particularly significant in languages like Japanese. It's a concept distinct from a syllable, playing a crucial role in the accentual system and poetic forms such as haiku. For instance, a Japanese word like kantō is perceived as four moras (ka, n, to, o) rather than two syllables (kan, tō).12

Moras can be formed by vowels, but also by nasal consonants or the first consonant of a double consonant. Long vowels count as two moras. In poetry, lines are often measured by the number of moras, with a haiku having a 5-7-5 mora structure. The mora is also a unit of measure in quantitative verse, equivalent to the time of a short syllable.123