unfaithful vs faithless

unfaithful and faithless both are adjectives.

Word	Noun	Adjective	Verb	Adverb
unfaithful	No	Yes	No	No
faithless	No	Yes	No	No

As adjectives, unfaithful and faithless are synonyms defined as:

unfaithful and faithless: having the character of, or characteristic of, a traitor

Other synonyms of unfaithful include traitorous, treasonable, treasonous.

unfaithful (adjective)	faithless (adjective)
not true to duty or obligation or promises	having the character of, or characteristic of, a traitor
having sexual relations with someone other than your husband or wife, or your boyfriend or girlfriend
having the character of, or characteristic of, a traitor
not trustworthy