IPA: /ˌpærəˈnɔɪə/
KK: /pærəˈnɔɪə/
A mental condition where a person feels extreme and unreasonable distrust or suspicion of others, often believing that they are being harmed or persecuted.
His paranoia made it difficult for him to trust anyone around him.
Paranoia is derived from the Greek "para-" (meaning beside or beyond) and "noia" (from "noein", meaning to think or perceive). The term originally referred to a condition of the mind that is characterized by irrational thoughts or perceptions that are beyond normal thinking.
Think of 'thinking beyond' ('para-') what is normal ('noia') — that's why paranoia refers to irrational thoughts or perceptions.