affinal vs affine

affinal

adj
  • Of a family relationship by marriage of a relative (or through affinity), as opposed to consanguinity; in-law. 

affine

adj
  • Of two materials, having mutual affinity. 

  • Of or pertaining to a function expressible as f(⃑x)=A⃑x+⃑b (where A is a linear transformation and ⃑b is a constant), which, regarded as a transformation, maps parallel lines to parallel lines and finite points to finite points. 

  • Assigning finite values to finite quantities. 

verb
  • To refine. 

noun
  • A relative by marriage. 

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