Tributary
Part of speech: noun
Definition: A river that flows into a larger river or other body of water. A nation, state, or other entity that pays tribute.
Part of speech: adjective
Definition: Related to the paying of tribute.
Confluence
Part of speech: noun
Definition: The place where two rivers, streams, or other continuously flowing bodies of water meet and become one, especially where a tributary joins a river.The act of combining which occurs at the place where rivers and the like meet.A convergence or combination of forces, people, or things.