Kōsen-rufu (広宣流布) is a phrase found in the Japanese translation of the Lotus Sutra. Kōsen means to "widely declare." "Widely" implies speaking out to the world, to an ever-greater number and ever-broader spectrum of people. "Declare" means to proclaim one's ideals, principles and philosophy. The ru (flow) of rufu means "a current like that of a great river," and fu (cloth) means "to spread out like a bolt of cloth."
Figuratively, it means to declare and spread widely [the teachings of the Buddha]. According to Soka Gakkai, a modern Buddhist movement based on the teachings of Nichiren (1222–1282), Nichiren stressed kōsen-rufu in Buddhist practice because he felt that personal enlightenment was interrelated to the peace and well-being of the entire society.