forgiveness vs mercy

forgiveness and mercy both are nouns.

Word	Noun	Adjective	Verb	Adverb
forgiveness	Yes	No	No	No
mercy	Yes	No	No	No

As nouns, mercy is a hypernym of forgiveness; that is, mercy is a word with a broader meaning than forgiveness:

Other hypernyms of forgiveness include mercifulness.

forgiveness (noun)	mercy (noun)
the act of excusing a mistake or offense	leniency and compassion shown toward offenders by a person or agency charged with administering justice
compassionate feelings that support a willingness to forgive	alleviation of distress; showing great kindness toward the distressed
	a disposition to be kind and forgiving
	the feeling that motivates compassion
	something for which to be thankful