kidnaper vs felon

kidnaper and felon both are nouns.

Word	Noun	Adjective	Verb	Adverb
kidnaper	Yes	No	No	No
felon	Yes	No	No	No

As nouns, felon is a hypernym of kidnaper; that is, felon is a word with a broader meaning than kidnaper:

kidnaper: someone who unlawfully seizes and detains a victim (usually for ransom)
felon: someone who has committed a crime or has been legally convicted of a crime

Other hypernyms of kidnaper include captor, capturer, criminal, crook, malefactor, outlaw.

kidnaper (noun)	felon (noun)
someone who unlawfully seizes and detains a victim (usually for ransom)	someone who has committed a crime or has been legally convicted of a crime
	a purulent infection at the end of a finger or toe in the area surrounding the nail