Merriam-Webster Collegiate Dictionary - psychology

 noun  (plural -gies)  Etymology: New Latin psychologia, from psych- + -logia -logy  Date: 1653  1. the science of mind and behavior  2.  a. the mental or behavioral characteristics of an individual or group  b. the study of mind and behavior in relation to a particular field of knowledge or activity  3. a theory or system of ~ Freudian ~ the ~ of Jung  • psychologist noun