In classical-conditioning situations, the is unlearned, but the is learned.

The unconditioned response is unlearned, but the conditioned response is learned. An example would be a dog salivating as a response to food. The salivation would be the conditioned response. When the dog eventually starts salivating to the rattling of a bag of dog food which it has been hearing every time before it is fed, this salivation in response to the rattling sound is the conditioned response.