faithlessly vs false

faithlessly is not an adjective while false is an adjective.

Word	Noun	Adjective	Verb	Adverb
faithlessly	No	No	No	Yes
false	No	Yes	No	Yes

As adverbs, faithlessly and false are synonyms defined as:

Other synonyms of faithlessly include traitorously, treacherously, treasonably.

faithlessly (adjective)	false (adjective)
	not in accordance with the fact or reality or actuality
	not genuine or real; being an imitation of the genuine article
	adopted in order to deceive
	designed to deceive
	(used especially of persons) not dependable in devotion or affection; unfaithful
	arising from error
	inaccurate in pitch
	deliberately deceptive
	erroneous and usually accidental
	inappropriate to reality or facts

faithlessly (adverb)	false (adverb)
in a disloyal and faithless manner	in a disloyal and faithless manner