Which term refers to a stream or river that flows into a larger river?

The term that refers to a stream or river flowing into a larger river is "tributary." This term specifically describes the relationship between two water bodies, where the tributary contributes its flow to the larger river, which is often referred to as the main or parent river. Understanding this concept is important because tributaries play a crucial role in the hydrology of an area, affecting water flow, ecosystems, and sediment transport. In contrast, an estuary is a coastal area where freshwater from rivers and streams meets and mixes with saltwater from the ocean, while a confluence is the point at which two rivers meet, and a delta is a landform that forms at the mouth of a river where it deposits sediment as it flows into another body of water, typically an ocean or a sea.