Faith is often used in a religious context, as in theology, where it almost universally refers to a trusting belief in a transcendent reality, or else in a Supreme Being and said being's role in the order of transcendent, spiritual things. In Christianity it derives from the Greek pistis or root word peitho, meaning to trust, to have confidence, faithfulness, reliable, to assure. In the Jewish scriptures it refers to how God acts toward His people and how they are to respond to him. ( Edited by plmiller )  

http://en.wikipedia.org/wiki/Deity