There is no "minimum length" to be classified as a river. However, width, and to a lesser extent depth do figure into whether or not it is called a river. If one can toss a rock across it, and it is...
The word Niagara (modern English pronunciation nai-æg-era) is believed to be derived from the Mohawk word "ohnyákara", meaning 'neck of land (between the lakes)
From its source to its mouth. .............................................................................. If you didn't find that helpful, which most of you should not, the longest river is the...