What do trait terms such as introversion and extraversion represent?

A) linguistic conventions for describing otherwise indescribable qualities
B) anchor points, or contrasting qualities, of a personality dimension
C) unconscious motivations that guide behavior
D) theoretical constructs in need of scientific validation

Trait terms such as introversion and extraversion are anchor points or contrasting qualities of a personality dimension, specifically the Big Five personality traits. This dimension is also known as the extraversion-introversion dimension and describes an individual's levels of sociability, assertiveness, and positive emotionality. Researchers use these terms to capture and measure the trait differences among individuals.