What does "tributary" mean?

Additional senses

1. 2.Paid in tribute. "Tributary tears." Shak.
2. 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; as, the Ohio has many tributary streams, and is itself tributary to the Mississippi.
3. 4.A ruler or state that pays tribute, or a stated sum, to a conquering power, for the purpose of securing peace and protection, or as an acknowledgment of submission, or for the purchase of security.
4. 5.A stream or river flowing into a larger river or into a lake; an affluent.