psychology

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun The science that deals with mental processes and behavior.
• noun The emotional and behavioral characteristics of an individual, group, or activity.
• noun Subtle tactical action or argument used to manipulate or influence another.
• noun Philosophy The branch of metaphysics that studies the soul, the mind, and the relationship of life and mind to the functions of the body.

from The Century Dictionary.

• noun The special psychology of any single group of living things: a common term for folk psychology, professional psychology, race psychology, ethnic psychology, psychology of peoples, etc.
• noun The science of the products of the mental life in the human race at large; same as folk psychology .
• noun The psychology and psychogenesis of the human mind.
• noun Race psychology; the differential psychology of species and races, whether human or sub-human.
• noun The science of the individual mind as conditioned, in its functions and development, by other minds; the psychology of the social factor in its influence upon the individual mind.
• noun The science of the phenomena of mind; mental science.

from the GNU version of the Collaborative International Dictionary of English.

• noun The science of the human soul; specifically, the systematic or scientific knowledge of the powers and functions of the human soul, so far as they are known by consciousness; a treatise on the human soul.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun uncountable The study of the human mind.
• noun uncountable The study of human behavior.
• noun uncountable The study of animal behavior.
• noun countable The mental, emotional, and behavioral characteristics pertaining to a specified person, group, or activity.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun the science of mental life