1. An extreme, irrational, and unreasonable suspicion or distrust of other people and their motives.
2. A psychiatric disorder characterized by an elaborate, overly suspicious system of thinking which often includes delusions of persecution and grandeur usually centered on one major theme; such as, a financial matter, a job situation, an unfaithful spouse, or another problem including being followed or monitored by a governmental intelligence agency; by outer space aliens; being the victim of computer tampering; or of being poisoned.
3. A condition in which patients show persistent persecutory delusions or delusional jealousy, with emotion and behavior appropriate to the content of the delusional system. 4. Etymology: "mental disorder characterized by systematized delusions", 1891 (earlier paranoea 1811), from Greek paranoia, "mental derangement, madness,"; which came from paranoos, "mentally ill, insane", from para-, "beside, beyond" + noos, "mind" and Greek noein, "to think".

The unfounded conviction that the patient's spouse or lover is unfaithful: "Such jealous-type paranoias can sometimes be so overwhelming that they make the relationships of such patients impossible."

Paranoia in which the patient institutes or threatens to institute legal action because of an imagined persecution.

The delusion that one's body is malodorous (stinks), or is infested with an internal or external parasite, or that his/her body is physically misshapen or unduly ugly.