Agreeableness, which reflects a consistently warm, prosocial, non-aggressive orientation toward others, is one of the Big Five dimensions of human personality uncovered by factor analyses of trait ratings in several languages and cultures. Like the other Big Five constructs, agreeableness is a higher order statistical factor reflecting a pattern of intercorrelation among a number of more specific traits, in this case involving an individual's approach to interpersonal relationships. Agreeableness appears to be a lifelong aspect of personality in that one's level of agreeableness relative to others tends to remain consistent over long periods of time, although people typically do become somewhat more agreeable as they age.

Source: The Encyclopedia of Positive Psychology