Here's why:
* It names a concept: Repression refers to the act of suppressing or inhibiting thoughts, feelings, or impulses.
* It can be the subject of a sentence: "Repression can have a negative impact on mental health."
* It can be the object of a verb: "The government used repression to silence its critics."
Let me know if you have any other words you'd like to identify the part of speech for!