River
River
Jet Stream
Jet Stream
A stream or river called that flows into a larger stream or river is called a tributary.
River
A small stream is called a creek.
The side of a stream is usually called its bank.
It is occasionally called a sinking stream or a disappearing stream, but geographers and geologists normally call it a stream, just like another stream.
Tributary is the answer you are looking for, I believe.
a waterway is a large stream
a tributary
a stream