The approach of many trait theorists has been to develop a set of core personality traits that encompass many others and use this set as the basis of a conceptual model. We will now explore several of these models. As one of the first contemporary trait theorists, Gordon Allport did some useful work in defining a trait, differentiating it from habits and attitudes, and categorizing different types of traits. Basically, Allport is saying that a disposition makes people respond to different situations with a similar behavior.
Habits also influence responses, but habits are responses to a single, specific situation.
Allport had two ways of categorizing traits. First, he broke them down into either individual traits or common traits. In the strictest sense, all traits are unique to the individual. With this in mind, Allport emphasized the importance of studying individual's on a personal basis to assess their personality. The other way Allport categorized traits was by their degree of influence and pervasiveness in an individual's personality.