The ancient Greek and Roman worlds made important contributions to both religion and philosophy, the study of the nature of truth, knowledge, and moral values. In fact the word philosophy is of Greek origin, combining the words philia or "to love" with sophia or "wisdom."...Greek and Roman religion was polytheistic; ancient Greeks and Romans worshipped many gods and goddesses. Devout members of both groups believed that there were gods who influenced all natural phenomena. Ancient Greeks developed elaborate myths, or stories that explained these phenomena in terms of how these deities behaved, their strengths and weaknesses, and their histories. Each Greek polis, or city-state (independent political units consisting of a city and the countryside around it) had its own set of important gods and goddesses and its own way to worship and honor them. Eventually most Greeks identified a pantheon (a group of all gods and goddesses) of twelve major deities.