定義：a channel, e.g., a fosse, canal, shaft; specifically the Nile, as the one river of Egypt, including its collateral trenches; also the Tigris, as the main river of Assyria
定義：to tend a flock; i.e., pasture it; intransitively, to graze (literally or figuratively); generally to rule; by extension, to associate with (as a friend)
