form class vs part of speech

form class and part of speech both are nouns.

Word	Noun	Adjective	Verb	Adverb
form class	Yes	No	No	No
part of speech	Yes	No	No	No

As nouns, form class and part of speech are synonyms defined as:

form class and part of speech: one of the traditional categories of words intended to reflect their functions in a grammatical context

Other synonyms of form class include word class.

form class (noun)	part of speech (noun)
one of the traditional categories of words intended to reflect their functions in a grammatical context	one of the traditional categories of words intended to reflect their functions in a grammatical context