Remember that conditioning is another term for learning.Any stimulus or response that is unconditioned,simply means unlearned,or before learning has taken place.
Some key terms in classical conditioning include:
Neutral stimulus (NS) - a stimulus which, prior to conditioning,would evoke no response.This always becomes the conditioned stimulus,e.g. the bell in Pavlov's experiments.
Unconditioned stimulus (UCS) - a stimulus which innately produces a response or reflex,such as the meat in Pavlov's experiments.
Unconditioned response (UCR) - an unlearned response elicited by an unconditioned stimulus,e.g. the dog involuntarily salivated at the meat (UCS).
Association - a connection between two events which results in learning.Pavlov's dogs learned to associate the ringing of the bell and the presentation of the meat so that they eventually learned to salivate at the bell alone.
Conditioned stimulus (CS) - After the neutral stimulus has been paired with the unconditioned stimulus many times,the neutral stimulus becomes the conditioned stimulus.It now elicits a learned response such as the bell.
Conditioned response (CR) - a learned response to a conditioned stimulus.Pavlov's dogs learned to salivate at the bell.