Final answer:
Personality theory analyzes the unique patterns of thinking, behavior, and emotion that comprise an individual's personality. Aggregation implies the stability and consistency of traits over time and situations. Personality theories may be nomothetic, which are universal, or idiographic, which are individualized.
Step-by-step explanation:
Personality theory addresses the patterns of thoughts, behaviors, and feelings that make an individual unique. Traits are characteristic ways of behaving, and trait theorists, such as Gordon Allport, have categorized these traits into three levels: cardinal traits, central traits, and secondary traits.
Aggregation refers to the idea that behaviors are consistent and stable over time and different situations that can be averaged to reveal a trait. Personality theories can be broadly classified as nomothetic, which focus on universal traits that can be applied to everyone, or idiographic, which are personalized and focus on individual differences.
Sigmund Freud's psychodynamic perspective is more idiographic, while the Five Factor Model of personality is nomothetic and widely accepted today, comprising openness, conscientiousness, extroversion, agreeableness, and neuroticism.