* Abstract nouns represent ideas, concepts, qualities, or states of being. They are not physical things you can touch or see.
* Childhood represents a period of time in a person's life, a stage of development. It's not a physical thing.
Examples of abstract nouns:
* Love
* Happiness
* Freedom
* Courage
* Time
* Beauty
In contrast, a concrete noun refers to something tangible, like a person, place, or thing.
Let me know if you have any other words you'd like to classify!