Faith was trust in a thing.
God travelled from planet to planet feeding on the faith of her worshippers. (AUDIO: Day Zero) She believed that faith was everything whilst Roy believed that it was cheap. (AUDIO: Eye of the Storm)
Reverend Wainwright struggled with his faith due to the British bombings of Germany. This let the Haemovores kill him.
Sorin had faith in the revolution.
The Seventh Doctor had faith in his companions, which was strong enough to repel the Haemovores. He had to break Ace's faith in him by belittling her, as her faith was the only thing keeping Fenric's influence active. (TV: The Curse of Fenric)
Torchwood Three believed that faith was key to defeating Duroc. (TV: Dead Man Walking)
The imprisoned Minotaur fed on faith. (TV: The God Complex)
The Sixth Doctor told Constance Clarke to have faith. She countered that he could not even find the TARDIS kitchen. (AUDIO: Shield of the Jötunn)