In psychology, grandiosity is a sense of superiority, uniqueness, or invulnerability that is unrealistic and not based on personal capability. It may be expressed by exaggerated beliefs regarding one's abilities, the belief that few other people have anything in common with oneself, and that one can only be understood by a few, very special people. Grandiosity is a core diagnostic criterion for hypomania/mania in bipolar disorder and narcissistic personality disorder.