The term "
On" (rarely "
Onji") refers to counting phonetic sounds in
Japanese poetry. In the Japanese language, the word "
on" (音) means "sound". It is used to mean the phonetic units counted in
haiku,
tanka, and
other such poetic forms. Known as "
morae" to English-speaking linguists, the modern Japanese term for the linguistic concept is either
haku () or
mōra ().