Question

can we use fastly as a adverb ???

Answer 1

➡️As well as being an adjective, fast is an adverb. We use it all the time as such: He ran fast.

➡️The "ly" ending is generally indicative of an adverb in English, but not all adverbs end in "ly", and not all words ending in "ly" are adverbs.

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Answer 2

No there's no need for fastly as fast is already an adverb and adjective and u can use fast in different sentences

For eg: I ran fast

Also even if slow take its suffix as - ly there is no need for fast to take it fastly.

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