1. Unconditioned Stimulus (UCS): Naturally triggers a response (e.g., food).
2. Unconditioned Response (UCR): Automatic response to UCS (e.g., salivation).
3. Neutral Stimulus (NS): Initially does not trigger a response (e.g., bell).
4. Conditioned Stimulus (CS): Previously neutral stimulus that triggers a learned response (e.g., bell after conditioning).
5. Conditioned Response (CR): Learned response to CS (e.g., salivation in response to bell).