Adverb is one of the parts of speech. An adverb qualifies the following-
He works hard.
He is very good.
She works very hard.
The fan was moving exactly over his head.
He hates him simply because he is very cunning.
A complete sentence
Luckily, everyone was safe.
In most of the cases adverbs are formed by adding ‘ly’, like slowly, gently, But not in all cases. Some words which end with ‘ly’ but are not adverbs are friendly, orderly, sickly, weekly, monthly. These words are adjectives.
Cowardly, Niggardly, Scholarly, Miserly are adjectives form. Their adverb can be made as ‘in a cowardly manner’, in a niggardly manner’, ‘in a miserly manner’, ‘in a scholarly manner’.
The words ‘late’, ‘hard’ and ‘free’ are adverb. If we add ‘ly’ to them, their meanings will change.
Adverbs seldom, never, nowhere, nothing, hardly, scarcely, neither, barely, rarely are negative in meaning. So, they should always used in the negative sense.