/ ˈtrɪbjətri; NAmE -teri/ noun
( pl. -ies ) a river or stream that flows into a larger river or a lake
► tribu·tary adjective [ only before noun ]:
a tributary stream
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WORD ORIGIN
late Middle English (originally referring to a person or state that pays tribute to another state or ruler): from Latin tributarius , from tributum , neuter past participle (used as a noun) of tribuere assign (originally divide between tribes), from tribus tribe. The current sense dates from the early 19th cent.