What term describes a small river that feeds into a larger river?

The term that describes a small river feeding into a larger river is "tributary." A tributary is a smaller stream or river that flows into a main river, contributing its water to the larger body of water. This relationship is crucial in geography as it helps in understanding river systems, drainage basins, and the hydrological cycle.

In a river system, tributaries play a significant role in increasing water volume and can affect the flow rate and overall health of the main river. Recognizing the importance of tributaries is essential for studying ecosystems, sediment transfer, and water management practices.

The other options represent types of water bodies but do not accurately depict the relationship of a smaller river contributing to a larger one. A stream may refer to any small flow of water, while a fork generally indicates a point where a river splits into two or more branches. A rivulet is simply a very small stream or brook, but it does not inherently imply the relationship of feeding into a larger river like tributary does.