noun vs major form class

noun and major form class both are nouns.

Word	Noun	Adjective	Verb	Adverb
noun	Yes	No	No	No
major form class	Yes	No	No	No

As nouns, major form class is a hypernym of noun; that is, major form class is a word with a broader meaning than noun:

noun: the word class that can serve as the subject or object of a verb, the object of a preposition, or in apposition
major form class: any of the major parts of speech of traditional grammar

noun (noun)	major form class (noun)
a content word that can be used to refer to a person, place, thing, quality, or action	any of the major parts of speech of traditional grammar
the word class that can serve as the subject or object of a verb, the object of a preposition, or in apposition