threefold vs trivalent

threefold

adj
  • triple 

  • three times as great 

adv
  • by a factor of three 

verb
  • To make threefold; to triple. 

noun
  • An algebraic variety of dimension 3. 

trivalent

adj
  • Having a valence of three. 

  • Protecting against three different (usually flu) viruses. 

noun
  • Any trivalent chromosome 

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