means The scientific study of the mind and behavior — how people think, feel, perceive, remember, and act.

from From Greek psyche, "soul" or "breath of life," plus -logia, "study of" — literally the study of the soul. The word was assembled in the 16th century in Latin form (psychologia) by European scholars; it didn't settle into its modern, science-of-the-mind sense until the 19th century, when laboratories replaced the soul with measurable behavior. Psyche herself, in myth, was a mortal woman so beautiful she was made into a goddess and married Love — a fitting ancestor for a field that keeps trying to pin down the unpinnable.