1 the scientific study of the human mind and its functions, esp. those affecting behaviour in a given context.
2 a treatise on or theory of this.
3 a the mental characteristics or attitude of a person or group. b the mental factors governing a situation or activity (the psychology of crime).
Derivatives:
psychologist n. psychologize v.tr. & intr. (also -ise).
Etymology: mod.L psychologia (as PSYCHO-, -LOGY)
Useful english dictionary. 2012.