If referring to a person:
* Minority: This refers to a group of people who are a smaller number than the majority.
* Youth: This refers to the state of being young, which is often associated with being a minor.
* Immaturity: This refers to the lack of maturity and experience, which is often associated with being a minor.
If referring to something small or insignificant:
* Triviality: This refers to something of little importance.
* Unimportance: This refers to the lack of significance or importance.
* insignificance: This refers to the quality of being unimportant or of little consequence.
The best abstract noun to use will depend on the specific meaning you are trying to convey.