Monotheism

Monotheism is the belief in only one god, rather than two or more, which would be polytheism. Many religions are monotheistic, such as Judaism, Christianity, Islam, Baha'i Faith, Sikhism, Eckankar, Zoroastrianism, deism, Cao Dai and Tenrikyo. Zoroastrianism is among the oldest monotheistic religions.

Other websites

• Stanford Encyclopedia of Philosophy