succour vs mercy

succour and mercy both are nouns.

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

As nouns, mercy is a hyponym of succour; that is, mercy is a word with a more specific, narrower meaning than succour:

succour: assistance in time of difficulty
mercy: alleviation of distress; showing great kindness toward the distressed

Other hyponyms of succour include comfort, consolation, solace.

succour (noun)	mercy (noun)
assistance in time of difficulty	leniency and compassion shown toward offenders by a person or agency charged with administering justice
	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

succour (verb)	mercy (verb)
help in a difficult situation