Very anthropological. A deity is something that is worshiped, and is a neutral term. A god is also a deity, and so is a goddess. Divinity is the essence of a quality that turns you into a deity. So Christians believe in the divinity of Jesus. So they believe that He, or he, is more than just a human. An old convention in English, now dying out, was that you if you were talking about the Biblical god, you would say God, and refer to Him as He or in capitals. This wasn’t done for the Greek gods, although their names would be capitalised.