Negative reinforcer refers to any event that, when terminated or prevented by a behavior, increases the rate of that behavior.
A Negative reinforcer is simply another form of a reinforcer and thus can be used in shaping, discrimination training, and conditioned reinforcement. Both Positive and Negative reinforcers increase the rate of a behavior, but a positive reinforcer is an event that is delivered, whereas a negative reinforcer is an event that is terminated or prevented. Negative reinforcer, moreover, is any stimulus whose removal or termination as the consequence of an act will increase the probability that the act will recur. In Operant conditioning, a stimulus - such as an electric shock - that increases the rate of response when removed.