coalescence vs unification

coalescence

noun
  • The act of coalescing. 

  • The merging of two segments into one. 

unification

noun
  • The act of unifying. 

  • Given two terms, their join with respect to a specialisation order. 

  • The state of being unified. 

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