Is the word waterfalls a noun?

Yes, "waterfalls" is a noun. It's a plural noun, referring to more than one waterfall.

Here's why:

* It names a thing: Waterfalls are a physical phenomenon.

* It can be the subject of a sentence: "The waterfalls were breathtaking."

* It can be the object of a verb: "We visited the waterfalls."

Let me know if you have any other word questions!