Source - The point where a river starts. The Mississippi with its source Lake Itasca at 450 m. above sea level in northern Minnesota.
The Mississippi is joined by the Illinois River and the Missouri River at Saint Louis, and by the Ohio at Cairo, Illinois. The Arkansas River joins the Mississippi in the state of Arkansas. Tributary – the Missouri joins the Mississippi. A small river that flows into a bigger river is a tributary.
Confluence – Where two rivers join. The Missouri flows into the Mississippi. The Big Muddy and The Mighty Mississippi. First explored 1804 by Lewis and Clark.
Channel – where a river flows. Often between two banks and on one bed. But not always.
Mississippi – flood plain with meaders and ox-bow lakes,
Mouth – the end of a river. The Mississippi has built a delta at its mouth.
The Mississippi flows into the Gulf of Mexico. Hurricanes occur here! The delta can be swamped by the sea.