then vs thereby

then

adv
  • In that case. 

  • Next in order of place. 

  • At that time. 

  • In addition; also; besides. 

  • At the same time; on the other hand. 

  • Used to contradict an assertion. 

  • Soon afterward. 

adj
  • Being so at that time. 

noun
  • That time 

thereby

adv
  • By it; by that; by that means, or as a consequence of that. 

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