Since the word 'fast' is both an adjective and an adverb, could I replace the word 'quickly' with 'fast' in a sentence?

Question

Example:

"Yes!" He said quickly.

If I replaced the word quickly in this excerpt with 'fast', would that be fine? Is it gramatically correct to write 'He said fast.'? It sounds weird to me but I wasn't too sure.

Answer 1

Hi Maximus,

In this case, replacing 'quickly' with 'fast' would be grammatically incorrect since 'quickly' describes this person's speaking as opposed to a physical action on their part.

The same would hold true for 'him' in the contexts of each of the following examples: "He responded quickly" versus "He responded fast"; "He told me that quickly" versus "He told me that fast". The latter sentences in each pair are incorrect for the same reason as the incorrect inclusion of "fast" in "He said fast".

I hope this helps!

Answer 2

I'm believe that the two words are interchangeable in your sentence in the strict grammatical sense. There is a sometimes a difference between what is grammatical and how we usually say things. One of the problems with your example might be a degree of confusion to the listener/reader. It could also mean that ". . . he said 'fast,'" as if he had said the word "fast." If I write a similar sentence, "He said it fast," that seems to sound more acceptable and also clarifies that something was said fast (in a fast manner).