v.
    - become smaller, fewer, or less; decrease. 
▸diminish in strength or quality; deteriorate.
 - politely refuse:
 the company declined to comment.
 - (especially of the sun) move downwards.
 - Grammar  state the forms of (a noun, pronoun, or adjective) corresponding to cases, number, and gender.
 
n.
  - a continuous loss of strength, numbers, or value.
 - archaic a disease in which the bodily strength gradually fails, especially tuberculosis.
 
 
  Derivative
  
    - declinable adj.
  - decliner n.
  - declining adj.
 
   
  Etymology
  ME: from OFr. decliner, from L. declinare ‘bend down, turn aside’, from de- ‘down’ + clinare ‘to bend’.