tributary
/ˈtrɪbjʊtərɪ/noun
(pl. -ies)
1
- a river or stream flowing into a larger river or lake（河川或湖泊的）支流：
the Illinois River, a tributary of the Mississippi.
伊利诺伊河, 密西西比河支流。
2
- historical a person or state that pays tribute to another state or ruler〈史〉进贡者; 附属国, 进贡国：
tributaries of the Chinese empire.
中国封建王朝的附属国。
词源
late Middle English (in sense 2)： from Latin tributarius, from tributum （see TRIBUTE）. Sense 1 dates from the early 19th cent.