This document provides definitions and descriptions of key terms related to rivers and river systems. It defines terms like headwaters, tributaries, meanders, floodplains, rapids, deltas, loads, watersheds, and more. It explains things like how headwaters are the source of the river, tributaries flow into larger streams, meanders follow winding paths on level land, floodplains are areas subject to seasonal flooding, and deltas form where rivers enter larger bodies of water.