root word vs descriptor

root word and descriptor both are nouns.

Word	Noun	Adjective	Verb	Adverb
root word	Yes	No	No	No
descriptor	Yes	No	No	No

As nouns, descriptor is a hypernym of root word; that is, descriptor is a word with a broader meaning than root word:

root word: (linguistics) the form of a word after all affixes are removed
descriptor: the phonological or orthographic sound or appearance of a word that can be used to describe or identify something

Other hypernyms of root word include form, signifier, word form.

root word (noun)	descriptor (noun)
(linguistics) the form of a word after all affixes are removed	a piece of stored information that is used to identify an item in an information storage and retrieval system
	the phonological or orthographic sound or appearance of a word that can be used to describe or identify something