Kathenotheism

Kathenotheism is the worship of one god at a time among many gods.  Therefore, it is possible to believe in many gods and to focus worship and service to one of them at a time (sequentially) depending on the needs and circumstances.  It can also mean that one God become supreme over another at different times.  Mormonism, for example teaches many gods exist but they worship and serve only one of them.