tributary

Short definition from Wiktionary

Noun

1. 1
   A natural water stream that flows into a larger river or other body of water.
2. 2
   A vein which drains into another vein.
3. 3
   A nation, state, or other entity that pays tribute.

Adjective

1. 1
   Related to the paying of tribute.
2. 2
   Subordinate; inferior.
3. 3
   Yielding supplies of any kind; serving to form or make up, a greater object of the same kind, as a part, branch, etc.; contributing.