When is a noun not a noun

When is a noun not a noun? Answer: when its an adjective. One of the ACTs favorite ways to play with you is to take words that normally act like nouns often professions such as author, architect, scientist, etc. and use them as adjectives. This might not seem like much of a big deal, or even something youd really need to pay attention to, except that it actually involves something the ACT absolutely loves to test: commas. Consider the following: You probably wouldnt write something like I.M. Pei is a celebrated, architect. Even if you dont know that famous is an adjective and that architect is a noun, you can probably feel that the comma is wrong there; theres no natural break in the sentence. But what about this? Glass is perhaps the building material most often associated with celebrated architect, I.M. Pei. Suddenly that comma seems like it could be ok. Perhaps you learned that you always put a comma before a persons name. Well, sometimes you do, but sometimes you dont. And this is one of those cases in which you dont. The reason is that architect, in this case, is being used to describe I.M. Pei. Even though architect looks like a noun, its acting as an adjective here. And since adjectives should never be separated from the nouns they describe by a comma, you do not need to place one between architect and I.M. Pei.