Curly was not bright but he made up for his dumbness by having the hardest head in world at least of Stooge movies. What part speech is dumbness?

Here's why:

* Noun: A noun is a word that names a person, place, thing, or idea. In this sentence, "dumbness" refers to the quality or state of being stupid.

Let me know if you'd like to know more about parts of speech!