Coward and Cowardly
Incorrect : You are a coward man.
Correct : You are a coward.
Incorrect : He behaves cowardly.
Correct : His behavior is cowardly.
Note : Coward is a noun, not an adjective. So you should use an article before it when it is singular,
Cowardly is not an adverb, but an adjective which modifies a noun.
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