2.NounThe act of declining a word; the act of listing the inflections of a noun, pronoun or adjective in order.
3.NounThe product of that act; a list of declined forms.
"a page full of declensions"
4.NounA way of categorizing nouns, pronouns, or adjectives according to the inflections they receive.
"In Latin, 'amicus' belongs to the second declension. Most second-declension nouns end in '-i' in the genitive singular and '-um' in the accusative singular."