serfdom vs slavery

serfdom and slavery both are nouns.

Word	Noun	Adjective	Verb	Adverb
serfdom	Yes	No	No	No
slavery	Yes	No	No	No

As nouns, slavery is a hypernym of serfdom; that is, slavery is a word with a broader meaning than serfdom:

Other hypernyms of serfdom include bondage, thraldom, thrall, thralldom.

serfdom (noun)	slavery (noun)
the state of a serf	work done under harsh conditions for little or no pay
	the practice of owning slaves
	the state of being under the control of another person