In pavlov's classical conditioning experiment, he presented the sound of a bell along with meat powder to his dogs. after several trials, the dogs learned to salivate to the sound of the bell in the absence of the meat powder. if pavlov's dogs did not salivate to a buzzer but only to a bell, then this phenomenon would be an example of

Conditioned stimulus

Classical conditioning is a learning procedure in which a biologically potent stimulus paired with previously neutral stimulus. This pairing will cause a response  that can be the same as the potent stimulus. This is done repeatedly for an organism to elicit a conditioned response to the previously neutral stimulus that was paired to the active stimulus. The dog salivates due to the idea that  food is related to the sound of the bell.