The term is tributary. It means that it contributes to the bigger stream.
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A tributary.
A Tributary
river
A stream can't reproduce, but it does replenish; since it flows from someplace and to another, it is constantly being renewed.
The mouth of a stream is where it meets a larger body of water, such as a lake, ocean, or another stream. It is where the stream's water flows out and mixes with the water of the larger body.
A stream or river called that flows into a larger stream or river is called a tributary.
A river is a large stream of fresh water that flows across land and empties into an ocean, lake, or some other body of water.
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