a small river or stream
A tributary or affluent is a stream or river that flows into a main stem (or parent) river or a lake. A tributary does not flow directly into a sea or ocean. Tributaries and the Main stem river serve...
An example is Neasho, that goes into the Arkansas river Located in Colorado, I beleive.
The Missouri and Ohio rivers are tributaries
an example of a tributary is a waterfall, like the Niagra Falls......<KiTKaT>......