declension

Etymology

From Middle English declenson, from Middle French declinaison (Modern French: déclinaison), from Latin dēclīnātiō. Doublet of declination.

noun

1. A falling off, decay or descent.
   Refinement of feeling, intellectual tastes, and a noble hospitality, were among the features of his character; and hoary years brought no mental declension, and drew no shade over the ardent affections by which he was distinguished, and in whose reciprocity, was his undeclining solace. 1845, Lydia Sigourney, Scenes in my Native Land, The Great Oak of Geneseo, page 86
2. (grammar) The act of declining a word; the act of listing the inflections of a noun, pronoun or adjective in order.
3. (grammar) The product of that act; a list of declined forms.
   a page full of declensions
4. (grammar) A 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.