contiguous vs vicinal

contiguous

adj
  • Adjacent; neighboring. 

  • Connected; touching; abutting. 

  • Connecting without a break. 

vicinal

adj
  • Of or pertaining to a neighborhood; neighboring. 

  • Describing identical atoms or groups attached to nearby (especially adjacent) atoms in a molecule. 

  • Describing subordinate planes on a crystal, which are very near to the fundamental planes in angles, and sometimes take their place. 

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