tangency vs vinculum

tangency

noun
  • The state of being tangent; an instance of (something) being tangent. 

vinculum

noun
  • A horizontal line over the top of some of the terms in an expression, indicating that that part of the calculation is to be done before other parts. 

  • A bond or link signifying union. 

  • A ligament that limits the movement of an organ or part. 

  • Specifically, the horizontal line between the numerator and denominator in a fraction. 

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