\De*clen"sion\, n. [Apparently corrupted fr. F.
d['e]clinaison, fr. L. declinatio, fr. declinare. See
{Decline}, and cf. {Declination}.]
1. The act or the state of declining; declination; descent;
   slope.
         The declension of the land from that place to the
         sea.                                  --T. Burnet.
2. A falling off towards a worse state; a downward tendency;
   deterioration; decay; as, the declension of virtue, of
   science, of a state, etc.
         Seduced the pitch and height of all his thoughts To
         base declension.                      --Shak.
3. Act of courteously refusing; act of declining; a
   declinature; refusal; as, the declension of a nomination.
4. (Gram.)
   (a) Inflection of nouns, adjectives, etc., according to
       the grammatical cases.
   (b) The form of the inflection of a word declined by
       cases; as, the first or the second declension of
       nouns, adjectives, etc.
   (c) Rehearsing a word as declined.
Note: The nominative was held to be the primary and original
      form, and was likened to a perpendicular line; the
      variations, or oblique cases, were regarded as fallings
      (hence called casus, cases, or fallings) from the
      nominative or perpendicular; and an enumerating of the
      various forms, being a sort of progressive descent from
      the noun's upright form, was called a declension.
      --Harris.
{Declension of the needle}, declination of the needle.