Basic:
* Psychology: The study of the mind and behavior.
* Psyche: The human soul, mind, or spirit.
* Psychic: Relating to the mind or the soul.
* Psychotic: Relating to a mental disorder characterized by a loss of contact with reality.
More complex:
* Psychopath: A person with a personality disorder characterized by antisocial behavior, lack of empathy, and remorse.
* Psychometry: The supposed ability to determine the history of an object by holding it.
* Psychopharmacology: The study of the effects of drugs on the mind and behavior.
* Psycholinguistics: The study of the relationship between language and the mind.
* Psychophysics: The study of the relationship between physical stimuli and psychological sensations.
* Psychosocial: Relating to the interaction of psychological and social factors.
Informal:
* Psyched: Excited or enthusiastic.
* Psych out: To trick or deceive someone.
Medical:
* Psychosis: A severe mental disorder characterized by a loss of contact with reality.
* Psychogenic: Originating in the mind.
* Psychotherapy: The treatment of mental disorders using psychological methods.
* Psychoanalyst: A therapist who practices psychoanalysis.
This is not an exhaustive list, as there are many other words that use the root "psych."