child vs descendant

child and descendant both are nouns.

Word	Noun	Adjective	Verb	Adverb
child	Yes	No	No	No
descendant	Yes	Yes	No	No

As nouns, descendant is a hypernym of child; that is, descendant is a word with a broader meaning than child:

Other hypernyms of child include descendent.

child (noun)	descendant (noun)
a young person of either sex	a person considered as descended from some ancestor
a human offspring (son or daughter) of any age
an immature childish person
a member of a clan or tribe

child (adjective)	descendant (adjective)
	going or coming down
	proceeding by descent from an ancestor