Paul Costa and Robert McCrae are psychologists who developed the Five-Factor Model (FFM) or "Big Five" model of personality traits.
One of the Big Five factors; it involves tendencies towards emotional instability, anxiety, moodiness, irritability, and sadness.
Another factor from Big Five; it refers to outgoingness, assertiveness, activeness, excitement-seeking behavior etc.
A part from Big Five model; it includes traits like imagination, insightfulness, wide array interests etc.