noun (n)

• a condition inferior to an earlier condition; a gradual falling off from a better state(noun.state)

  Synonym:
  decline
  Antonym:
  improvement, melioration
  

  source: wordnet30
• a downward slope or bend(noun.object)

  Synonym:
  declension, decline, declivity, descent, downslope, fall
  Antonym:
  acclivity, ascent, climb, raise, rise, upgrade
  

  source: wordnet30
• (astronomy) the angular distance of a celestial body north or to the south of the celestial equator; expressed in degrees; used with right ascension to specify positions on the celestial sphere(noun.location)

  Synonym:
  celestial latitude, dec
  

  source: wordnet30
• a polite refusal of an invitation(noun.communication)

  Synonym:
  regrets
  

  source: wordnet30
• The act or state of bending downward; inclination; as, declination of the head.(noun)

  source: webster1913