Question: “Are you brave enough to tackle ‘for free?’ Obviously it should be either ‘free,’ ‘free of charge’ or even ‘no charge.’ Teeth-on-edge-setting.” (Nancy Blackwell)
Answer: We better take care of this one fast. Chronic teeth-grinding is a good way to wind up with a root canal appointment or hearing loss. (If, like me, you were unaware that teeth grinding can cause hearing loss, I’m glad we could share this learning moment.)
The question: Is saying “for free,” as in, “I’d like some waffle fries, for free,” grammatically correct?
The answer: No, I’m afraid not. There are two very good reasons for this. The first: “For” and “free” are considered shortenings of the expressions “in exchange for” and “free of charge,” respectively. There are plenty of articles on the Internet discussing the issue here – namely that “in exchange for free of charge” doesn’t make much sense. I’ll leave it at this: “Free” means, by definition, “for nothing,” so to say “for for nothing” is entirely redundant.
The second reason: “For,” as a preposition, begs to start a prepositional phrase. To complete that goal, it needs a noun or pronoun to act as its object. But “free,” being an adverb in the sentence above, cannot fill that role. “Free” modifies “like,” leaving “for” dangling off the end of the sentence with no object and no purpose. There is a redundancy here too. The prepositional phrase that “for” tries to start would act as an adverb modifying “like.” For example, you might say, “I would like waffle fries for nothing.” But you would not say, “I would like waffle fries free for nothing,” which is what, if completed, the phrase “for” would say.
The message to take away here is that “for free” is, at best, a redundancy, and at worst a purposeless, dangling preposition – and nobody wants those hanging around when you have free waffle fries to enjoy.