The term 'PART OF A RIVER' can be solved by two crossword solutions: 'MOUTH' (5 letters) and 'FORK' (4 letters). The MOUTH of a river is the point where it meets the sea or another body of water. It is the end of the river, and is usually the widest part. A FORK in a river is a point where the river splits into two or more branches. This often happens when the river meets an obstacle, such as a rock or a mountain.