From Wiktionary, the free dictionary

From Middle English declinacioun, borrowed from Middle French declination, from Latin declinatio. Doublet of declension.

• IPA^(key): /ˌdɛklɪˈneɪʃən/
• Rhymes: -eɪʃən

declination (countable and uncountable, plural declinations)

1. At a given point, the angle between magnetic north and true north.

   Synonym: magnetic declination

2. At a given point, the angle between the line connecting this point with the geographical center of the earth and the equatorial plane.

   Synonym: δ

   Coordinate term: right ascension

3. A refusal.

   Synonyms: nonassent, denial, rejection; see also Thesaurus:disapproval

   • 1746, Arthur Collins, Letters And Memorials Of State In the Reigns of Queen Mary:

     the queen's declination from marriage

4. (linguistics, prosody) The gradual decline in the overall fundamental frequency or pitch of speech over the course of an utterance, independent of local variations such as tones and pitch accents.
5. (grammar, obsolete) Declension.
6. (archaic) The act or state of bending downward; inclination.

   declination of the head

7. (archaic) The act or state of falling off or declining from excellence or perfection; deterioration; decay; decline.
   • c. 1635, Edmund Waller, To My Young Lady Lucy Sidney:

     Summer […] is not looked on as a time of declination or decay.

8. (archaic) Deviation.

   • 1692, Richard Bentley, [A Confutation of Atheism] (please specify the sermon), London: [Thomas Parkhurst; Henry Mortlock], published 1692–1693:

     this declination of atoms in their descent

   • November 2, 1690, Robert South, Sinners Inexcusable from Natural Religion Only

     every violation of and declination from the rules

• codeclination
• declinational
• declination circle

• decline

• nonciliated