However, you might be asking about the word *italics* when it's used *in* a sentence. In that case, it's a little more complicated:
* If *italics* is being used to describe the style of printing, then it's an adjective. For example: "The title of the book was printed in *italics*."
* If *italics* is being used as a noun to refer to the style of printing itself, then it's a noun. For example: "The use of *italics* is common in scientific writing."
It all depends on the context!