In Japanese in a martial arts context: way, manner, style, fashion. A "stream" of transmission, particularly of an old martial arts tradition. Translating this word as school places too many westernized meanings to the word, the process of transmission would not resemble a modern school in most cases.

Derived from 流.

In Chinese this character literally means "stream of water" as in 河深流靜​, or other types of stream 氣流 (air current), or metaphorical streams like 意識流 (stream of consciousness). Other Japanese uses of 流 retain this basic meaning.