Extracted from The Oxford English Dictionary and The Oxford Companion to the Mind
Psyche: The soul or spirit, breath, life, mind, love; represented as having butterfly wings. A butterfly.
Psychic: One who is particularly susceptible to psychic or spiritual influence.
Psychiatry: The medical treatment of diseases of the mind; hence psychiatrist.
Psychosis: The misapprehension and misinterpretation of the nature of reality.