overlayer vs transparency

overlayer

noun
  • A layer of adatoms adsorbed onto a surface, as onto the surface of a single crystal. 

transparency

noun
  • A transparent object. 

  • Sufficient accuracy to make the compressed result perceptually indistinguishable from the uncompressed input. 

  • The quality of being transparent; transparence. 

  • A transparent artwork, viewable by shining light through it. 

  • A translucent film-like material with an image imprinted on it, viewable by shining light through it. 

  • Openness; accessibility to scrutiny. 

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