A trait is a major building block of a Sim's personality. Traits effectively determine a Sim's behaviors, abilities, and wishes. Traits often grant Sims specific abilities or allow Sims to perform specific actions. Sims are usually limited in the number of traits they can have, and certain traits cannot be held simultaneously by the same Sim.
Traits were introduced in The Sims 3, replacing the points-based personality system present in The Sims and The Sims 2. Traits have also been incorporated in The Sims Medieval, The Sims Social, and The Sims 4