dilute vs lighten

dilute

verb
  • To become attenuated, thin, or weak. 

  • To cause the value of individual shares or the stake of a shareholder to decrease by increasing the total number of shares. 

  • To weaken, especially by adding a foreign substance. 

  • To make thinner by adding solvent to a solution, especially by adding water. 

adj
  • Of an animal: having a lighter-coloured coat than is usual. 

  • Having a low concentration. 

  • Weak; reduced in strength by dilution; diluted. 

noun
  • An animal having a lighter-coloured coat than is usual. 

lighten

verb
  • To become light or lighter in weight. 

  • To become brighter or clearer; to brighten. 

  • To make less serious or more cheerful. 

  • 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 dilute and lighten occurred in a corpus of books? (source: Google Ngram Viewer )