Personality is a structure gathering interrelated behavioral, cognitive and emotional patterns that biological and environmental factors influence; these interrelated patterns are relatively stable over time periods, but they change over the entire lifetime. While there is no generally agreed-upon definition of personality, most theories focus on motivation and psychological interactions with the environment one is surrounded by. Trait-based personality theories, such as those defined by Raymond Cattell, define personality as traits that predict an individual's behavior. On the other hand, more behaviorally-based approaches define personality through learning and habits. Nevertheless, most theories view personality as relatively stable.

व्यक्तित्व (personality) आधुनिक मनोविज्ञान का बहुत ही महत्वपूर्ण एवं प्रमुख विषय है। व्यक्तित्व के अध्ययन के आधार पर व्यक्ति के व्यवहार का पूर्वकथन भी किया जा सकता है।