Why are the Ohio and Missouri rivers considered tributaries of the Mississippi river?

The Ohio and Missouri rivers are considered tributaries of the Mississippi River because they flow into it, contributing their water and sediment. The Ohio River merges with the Mississippi at Cairo, Illinois, while the Missouri River joins the Mississippi near St. Louis, Missouri. As tributaries, they play a crucial role in the hydrology of the Mississippi River system, influencing its flow and ecological health. Their watersheds also support diverse ecosystems and are vital for regional economies.