Agreement:
* "The teacher nodded in agreement when I answered the question correctly."
* "She nodded her head slowly, signaling that she understood."
Greeting:
* "He nodded to me as I walked past, but didn't say anything."
* "We nodded to each other in greeting across the crowded room."
Acknowledgement:
* "He nodded his head in acknowledgment of the applause."
* "The witness nodded to confirm the details of the story."
Other:
* "The dog nodded its head and wagged its tail, excited for a treat."
* "The tree branches nodded in the gentle breeze."
Let me know if you'd like more examples!