An adjective describes a noun or pronoun: "That boy is so bad"
An adverb describes a verb or anything apart from a noun and pronoun: "That boy speaks badly!"
Adverbs are used to answer how questions e.g. "How does he talk? - He talks loudly."
Flowers smell sweet or flowers smell sweetly, which is correct? Smell sweet is correct because we it describes the smell of flowers. Smell sweetly tells how a rose smells i.e. flowers do not have noses so they cannot smell!!
"Fresh bread smells great" (adjective) - I am describinng my opinion on fresh bread
"I smell terribly because I have a cold" (adverb) - I am not able to use my nose to smell things because of my cold.
No, that is not a deciding factor in the use of the word. You do understand that "reek" is the verb being modified, right? To say, "Why does this place reek so bad" is improper grammar. It has to be 'badly'.
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