Compare these sentences:

The driver in front shouldn't have stopped so sudden.

The driver in front shouldn't have stopped so suddenly.

The second sentence was taken from my book, but that was the first time I've ever seen. I'm more familiar with "so + adjective" form, such as "you are so beautiful, he's so handsome, etc."

So, both sentences above are correct?

  • The opinion essay was so well written, and so convincingly argued it got an A.
    – Mari-Lou A
    May 28, 2021 at 4:10
  • There are irregular adverbs e.g good--well, and flat adverbs, where the adjective and its adverb remain unchanged e.g fast-- fast (not fastly) and slow --slow ( but also slowly). The adjective sudden follows the normal pattern ), i.e the suffix "ly" is added.
    – Mari-Lou A
    May 28, 2021 at 4:16
  • "So" can modify an adjective used as a predicative complement ("He was so nice"), but not an adverb. In your example "sudden(ly)" modifies the verb "stopped", and thus must be an ly adverb modified by the optional modifier "so".
    – BillJ
    May 28, 2021 at 5:25

2 Answers 2


"so" can indeed be used with either an adjective or an adverb to make it stronger. Your second sentence is grammatically correct. Your first sentence is wrong because you are using an adjective to describe the verb "stop". We stop suddenly (adverb), not sudden (adjective). You sing well (adverb), not good (adjective).

This page has games and examples to help you with adverbs, and there's a useful page on the use of "so" and "such" here.


Only the second sentence is correct. You can use an adverb after "so", and you must if the phrase is modifying the verb. The word "so" will have the same sense, indicating, more or less, to a previously indicated or implied degree.

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .