Monotheism: The belief in one God (mono-theos) as opposed to belief in many gods (polytheism). Although monotheists may acknowledge the reality of other supernatural powers (such as angels and demons), they believe that all such powers are ultimately under the control or authority of the one God who alone is supreme. Monotheism in its various forms is the teaching of Judaism, Christianity and Islam.1
1. Stanley J. Grenz, David Guretzki & Cherith Fee Nordling, Pocket Dictionary of Theological Terms (Downers Grove, IL: InterVarsity Press, 1999), p. 81.