[ sahy-koh ]
/ ˈsaɪ koʊ /
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See synonyms for: psycho / psychos on Thesaurus.com

noun, plural psy·chos.
a psychopathic or psychotic person.
a crazy or mentally unstable person.
psychopathic or psychotic.
crazy; mentally unstable.
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Origin of psycho

First recorded in 1935–40; by shortening

Other definitions for psycho (2 of 2)


a combining form representing psyche (psychological) and psychological (psychoanalysis) in compound words.
Also especially before a vowel, psych-.

Origin of psycho-

<Greek, combining form of psȳchḗ breath, spirit, soul, mind; akin to psȳ́chein to blow (see psykter)
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2023


What does psycho- mean?

Psycho– is a combining form used like a prefix meaning either “psyche” or “psychological.” Psyche denotes “the human soul, spirit, or mind,” while psychological is a related yet distinct term that means “pertaining to psychology, the science of the mind or of mental states.” Psycho– is often used in medical and technical terms, especially in psychology.

Psycho– comes from Greek psȳchḗ, meaning “breath, spirit, soul, mind.” For more on the meaning of this word in Ancient Greek mythology, read our entry for psyche. The word psyche is at the root of the term psychedelic, which refers to the effect of hallucinogenic drugs.

What are variants of psycho-?

When combined with words or word elements that begin with a vowel, psycho– becomes psych, as in psychiatry. Want to know more? Read our Words That Use article on psych-.

Examples of psycho-

An example of a word you may have encountered that features psycho– is psychopathy, “a mental disorder in which an individual manifests amoral and antisocial behavior, lack of ability to love or establish meaningful personal relationships, extreme egocentricity, failure to learn from experience, etc.”

While psycho– means “psyche,” the pathy portion of the word refers to “disease,” from Greek pátheia, meaning “suffering.” Psychopathy literally means “disease of the psyche (mind).”

What are some words that use the combining form psycho-?

What are some other forms that psycho– may be commonly confused with?

Break it down!

The combining form metrics means “the science of measuring.” With this in mind, what is the field of psychometrics?

How to use psycho in a sentence

British Dictionary definitions for psycho (1 of 2)

/ (ˈsaɪkəʊ) /

noun, adjective plural -chos
an informal and offensive word for psychopath or psychopathicSee psychopath

British Dictionary definitions for psycho (2 of 2)


sometimes before a vowel psych-

combining form
indicating the mind or psychological or mental processespsychology; psychogenesis; psychosomatic

Word Origin for psycho-

from Greek psukhē spirit, breath
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012