In the context of operant conditioning, reinforcement and punishment serve opposite functions in modifying behavior. The primary goal of reinforcement is to increase the likelihood that a behavior will be repeated, either by adding a desirable stimulus (positive reinforcement) or removing an undesirable one (negative reinforcement). Conversely, the goal of punishment is to decrease the likelihood of a behavior, either by adding an aversive stimulus (positive punishment) or removing a desirable one (negative punishment).