singular form vs signifier

singular form and signifier both are nouns.

Word	Noun	Adjective	Verb	Adverb
singular form	Yes	No	No	No
signifier	Yes	No	No	No

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

singular form: the form of a word that is used to denote a singleton
signifier: the phonological or orthographic sound or appearance of a word that can be used to describe or identify something

Other hypernyms of singular form include descriptor, form, word form.

singular form (noun)	signifier (noun)
the form of a word that is used to denote a singleton	the phonological or orthographic sound or appearance of a word that can be used to describe or identify something