noun vs declension

noun and declension both are nouns.

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

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