Qu (fermentation starter)

A grain starter for fermentation. 麴 is grain cultured with molds, whose enzymes turn starch into sugars for fermentation.

An early wine-making line in the Shangshu, a Chinese classic, pairs 麴 with 蘖, a character for sprouted grain. The Shuowen Jiezi, an early Chinese dictionary, glosses a related form as “wine starter.” The exact modern glyph 麴 is absent from that entry.

Later uses include starters for rice wine, Chinese spirits, soy sauce, miso, and other fermentations. In Japanese, 麹 is the conventional form related to older 麴.

Is 麴 the same as 麯, 麹, or 曲?

麯 and 麹 are related spellings; 曲 depends on context. 麯 is a Chinese variant of 麴. Japanese uses 麹 as its conventional form, while 麴 is the older form.

Traditional Chinese writes 酒麴; simplified Chinese writes 酒曲. On its own, 曲 can mean a bend or a tune, so the surrounding word tells you which sense applies.