What part of speech is caustic?

"Caustic" can be a few different parts of speech, depending on how it's used:

* Adjective: Describing something that is harshly critical, sarcastic, or corrosive.

* Example: "She made a caustic remark about his new haircut."

* Noun: Referring to a substance that can burn or corrode.

* Example: "The caustic solution etched away the metal."

So, the part of speech depends on the context of the sentence!