then vs thenceforth

then

adv

  • At that time. 

  • Next in order of place. 

  • In addition; also; besides. 

  • At the same time; on the other hand. 

  • Used to contradict an assertion. 

  • In that case. 

  • Soon afterward. 

noun

  • That time 

adj

  • Being so at that time. 

thenceforth

adv

  • From that time on. 

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