A delusion is a belief that is clearly false (non bizarre) ;due to abnormality in the affected person's content of thought. The false belief is not due to person’s cultural or religious background or his or her level of intelligence. It is the degree to which the person is convinced that the belief is true. A person with a delusion will hold firmly to the belief regardless of contrary evidence. Some delusions are:
Delusion of control: This is a false belief that another person, group of people, or external force controls one's thoughts, feelings, impulses, or behavior. A person may describe, for instance, the experience that aliens actually make him or her move in certain ways and that the person affected has no control over the bodily movements.
Delusional jealousy: A person with this delusion falsely believes that his or her spouse or lover is having an affair. This delusion stems from pathological jealousy and the person often gathers "evidence" and confronts the spouse about the nonexistent affair.
Delusion of guilt or sin: This is a false feeling of remorse or guilt of delusional intensity. A person may, for example, believe that he or she has committed some horrible crime and should be punished severely. Another example is a person who is convinced that he or she is responsible for some disaster (such as fire, flood, or earthquake) with which there can be no possible connection.
Delusion of mind being read: This is a false belief that other people can know one's thoughts. This is different from thought broadcasting in that the person does not believe that his or her thoughts are heard aloud.
There is a subtle difference between illusion and delusion.