Which is the best definition of a delusion?

Fixed false belief A delusion is a fixed, false belief that is not in keeping with a patient's cultural background. The perceptual misrepresentation of a real sensory image is an illusion. The perceptual representation of a sound or an image that is not actually present is a hallucination. A pathological self-preoccupation is the definition of egomania. A dissociative fugue is a state in which patients travel away from their homes or work and assume new identities or occupations while forgetting impoant aspects and details of their former lives.