since vs though

since

conj
  • Because. 

  • From the time that. 

adv
  • From a specified time in the past. 

prep
  • At certain points during that period of time. 

  • Continuously during that period of time. 

though

conj
  • Despite the fact that; although. 

adv
  • Used to intensify statements or questions; indeed. 

  • Despite that; however. 

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