A delusion is a false belief held by a person. If doctors talk about delusions they mean that the false belief is the result of some disease, usually a disease of the mind, such as "paranoia", "schizophrenia" or "bipolar disorder, but not always neccesarily, delusions can come in many different forms such as political differences, economic differences such as a god complex upheld by someone who believes they are all powerful and many other types."