declension (Noun) — The inflection of nouns and pronouns and adjectives in Indo-European languages.
declension (Noun) — Process of changing to an inferior state.
declension (Noun) — A downward slope or bend.
declension (Noun) — A class of nouns, pronouns or adjectives in Indo-European languages having the same (or very similar) inflectional forms. ex. "the first declension in Latin"