decrease vs lighten

decrease

verb
  • To make (a quantity) smaller. 

  • Of a quantity, to become smaller. 

noun
  • A reduction in the number of stitches, usually accomplished by suspending the stitch to be decreased from another existing stitch or by knitting it together with another stitch. See Decrease (knitting). 

  • An amount by which a quantity is decreased. 

lighten

verb
  • To make less serious or more cheerful. 

  • To become light or lighter in weight. 

  • To become brighter or clearer; to brighten. 

  • To illuminate with knowledge; to enlighten. 

  • To descend; to light. 

  • To emit or disclose in, or as if in, lightning; to flash out, like lightning. 

  • To alleviate; to reduce the burden of. 

  • To become less serious or more cheerful. 

  • To make brighter or clearer; to illuminate. 

  • To make light or lighter in weight. 

How often have the words decrease and lighten occurred in a corpus of books? (source: Google Ngram Viewer )