Although the two share many characteristics, there are some differences. Alligators and crocodiles both have a pair of large teeth near the front of the lower jaw for hunting prey. In the crocodile, these two teeth remain visible when the jaw is closed. In alligators, these two teeth are hidden when the jaw is closed. In addition, the alligator's snout is much broader than the crocodile's.
Alligators are also much less aggressive and slower moving than crocodiles.
Macmillan Illustrated Animal Encyclopedia . Macmillan Publishing Co., 1984. World Book Encyclopedia .