the class of all items that can be substituted into the same position (or slot) in a grammatical sentence (are in paradigmatic relation with one another)
a class of nouns or pronouns or adjectives in Indo-European languages having the same (or very similar) inflectional forms; "the first declension in Latin"
a family of fifty or more genes on the sixth human chromosome that code for proteins on the surfaces of cells and that play a role in the immune response