In monotheistic belief systems, God is usually viewed as the supreme being, creator, and principal object of faith. In polytheistic belief systems, a god is "a spirit or being believed to have created, or for controlling some part of the universe or life, for which such a deity is often worshipped". Belief in the existence of at least one god is called theism.

A deity or god is a supernatural being considered to be sacred and worthy of worship due to having authority over the universe, nature or human life. The Oxford Dictionary of English defines deity as a god or goddess, or anything revered as divine. C. Scott Littleton defines a deity as "a being with powers greater than those of ordinary humans, but who interacts with humans, positively or negatively, in ways that carry humans to new levels of consciousness, beyond the grounded preoccupations of ordinary life".