Final answer:
A stream or river that flows throughout the year is classified as perennial. Perennial streams maintain water flow year-round in contrast to ephemeral streams, which only flow temporarily after rainfall.
Step-by-step explanation:
A stream or river that flows all year is referred to as perennial. Unlike ephemeral streams that flow only briefly during and following precipitation, perennial streams have water in their channels throughout the year. A tributary, on the other hand, is a smaller stream or river that flows into a larger one.
Rivers and streams are essential components of the hydrologic cycle, transporting surface runoff from the source, or headwaters, to the mouth at a lake or ocean. The characteristics of rivers and streams, known as abiotic features, can change along the course, with the source water often being cold, low in nutrients, and clear, and the flow rate changing depending on the width of the channel and the elevation of the headwaters.