Jian Jia in Qin Customs of The Book of Songs contains reiterative sentences like "Going against the current" and "Going with the current", whose difference was before not clear. This article argues that "su" originally means "tending towards"; "hui", "going against the current"; and "you", "going with the current". So, "su hui" indicates that the poet goes in the direction against the current while "su you" is just the opposite.
