Henotheism

Henotheism is the adherence to one particular god out of several, especially by a family, tribe, or other group.
Henotheism is sometimes defined as a monotheistic belief within a polytheistic world - believing that one god, or articulation of God, is better or clearer than others. Alternatively, henotheism is the worship of one god above an acknowledged pantheon. An example of this second form is the worship of a tribal god.
A henotheist would admit that many gods have real existence and are able to be worshipped. However the henotheist chooses to worship only one of these gods. This sets the henotheist apart from the polytheist who worships many gods.