Answer:
The three religions of Judaism, Christianity and Islam readily fit the definition of monotheism, which is to worship one god while denying the existence of other gods. But, the relationship of the three religions is closer than that: They claim to worship the same god. While Judaism gave that god a name, “Yahweh,” both Christianity and Islam simply refer to him as “God” -- in Arabic, Islam’s founding language, “Allah” means “The God.”
