D defs.my
Entry 4 senses Webster, 1913

Declension

/dək-lĕn'-shən/ · De·clen·sion · IPA /dɪˈklɛn.ʃən/
01 n. The act or the state of declining; declination; descent; slope.
  1. 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. 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. 3.
    Act of courteously refusing; act of declining; a declinature; refusal; as, the declension of a nomination.
  4. 4.
    Inflection of nouns, adjectives, etc., according to the grammatical cases.(Gram.)
Phrases & compounds
Declension of the needle — declination of the needle.