root word vs signifier

root word and signifier both are nouns.

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

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

root word: (linguistics) the form of a word after all affixes are removed
signifier: 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 descriptor, form, word form.

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