Neutral Stimulus: does not bring about response before conditioning
Unconditioned Stimulus: naturally brings about a response
Unconditioned Response: natural response
Conditioned Stimulus: previously neutral, paired with UCS to bring response
Conditioned Response: response that follows previously neutral stimulus
The response to this is called the unconditioned response (or UCR). The neutral stimulus (NS) is a new stimulus that does not produce a response.
Once the neutral stimulus has become associated with the unconditioned stimulus, it becomes a conditioned stimulus (CS). The conditioned response (CR) is the response to the conditioned stimulus.