Temperament
One's temperament was their overall attitude and type of emotional reaction to various stimuli.
In 2266, Spock noted that although James T. Kirk's double differed in temperament (namely lacking the captain's capacity for impulse control), they nonetheless had access to the same knowledge of the USS Enterprise, and therefore his actions were predictable. (TOS: "The Enemy Within")
In 2269, when Janice Lester in Kirk's body questioned why Lester would want to exchange bodies with Kirk, Kirk in Lester's body argued that Lester sought, among other things, "to attain a position (starship captain) she doesn't merit by temperament or training." (TOS: "Turnabout Intruder")
In 2375, Seven of Nine introduced One to B'Elanna Torres, characterizing the Klingon as having a volatile temperament. (VOY: "Drone")