People:
* child
* woman
* man
* teacher
* student
* friend
Animals:
* cat
* dog
* bird
* fish
* elephant
* butterfly
Things:
* book
* chair
* table
* car
* house
* computer
Places:
* city
* country
* park
* museum
* school
* restaurant
Concepts:
* love
* peace
* happiness
* freedom
* justice
* knowledge
Remember: Singular nouns refer to one person, place, thing, or idea.
Let me know if you'd like more examples or have any other questions!