When is a noun noun?

This is a bit of a tricky question, playing on the fact that "noun" is both a noun and a part of speech!

Here's how to break it down:

* "Noun" as a noun: This refers to the word itself, like when you say "Noun is a part of speech."

* "Noun" as a part of speech: This refers to the function of a word in a sentence. Nouns are words that name people, places, things, or ideas.

So, to answer your question, "noun" is a noun when it's referring to the word itself.

Let me know if you'd like to explore other aspects of nouns!