What does "downstream" refer to in relation to flow?

In the context of flow, "downstream" refers to the direction that fluid, such as water in a river or stream, naturally travels as it moves away from its source. This means that downstream is synonymous with the movement in the same direction as the flow. The correct answer accurately conveys this understanding of fluid dynamics.

In most contexts, including rivers and plumbing systems, the direction of flow is typically defined from the starting point, or the source, toward the endpoint where the fluid exits or is discharged. Therefore, "downstream" directly indicates moving away from the source, clarifying the relationship between flow and direction.