tributary
n. countablen. a smaller river or stream that flows into a larger one. It can also describe a smaller blood vessel that joins a larger one in your body.
n. a stream or river that flows into a larger main stem or a lake; in anatomy, a smaller vein or lymphatic vessel that empties into a larger trunk.
The Missouri River is a major tributary of the Mississippi.
Heavy rainfall in the mountains caused every small tributary to swell, eventually flooding the main river valley downstream.
The surgeon carefully mapped the vascular network, identifying each minor tributary that fed into the primary vein to prevent excessive bleeding during the procedure.
PIE word *tréyes From Middle English tributarie (“paying tribute”), from Latin tribūtārius, from tribūtum (“tribute”).
Often used with the preposition 'of' to indicate the larger body of water or vessel it joins.