General:
* Youth
* Yearning
* Yonder (can be abstract when referring to a vague distant place)
* Yield (as in the outcome or result of something)
* Yoke (as in the burden or constraint)
More specific:
* Yearning
* Yawn (the feeling of drowsiness)
* Yuck (the feeling of disgust)
* Yes (a state of agreement or confirmation)
* Yodel (the act of singing in a particular way)
Note: Some words may be considered abstract nouns in certain contexts but not others. For example, "yearning" can be considered abstract but "year" is concrete.
Let me know if you'd like me to explore any specific category of abstract nouns!