This document discusses different theories of personality traits. It describes trait theories proposed by Allport, Eysenck, Cattell, and the Big Five model. Allport defined traits as stable neuropsychic structures that influence behavior consistently across situations. Eysenck distinguished between traits and types, with types comprising sets of correlated traits. Cattell proposed surface and source traits. The Big Five model describes the five broad traits of Extraversion, Agreeableness, Neuroticism, Conscientiousness, and Openness.