declension vs noun

declension and noun both are nouns.

Word	Noun	Adjective	Verb	Adverb
declension	Yes	No	No	No
noun	Yes	No	No	No

declension (noun)	noun (noun)
a class of nouns or pronouns or adjectives in Indo-European languages having the same (or very similar) inflectional forms	a content word that can be used to refer to a person, place, thing, quality, or action
a downward slope or bend	the word class that can serve as the subject or object of a verb, the object of a preposition, or in apposition
process of changing to an inferior state
the inflection of nouns and pronouns and adjectives in Indo-European languages