convex vs sunken

convex

adj
  • arranged such that for any two points in the set, a straight line between the two points is contained within the set. 

  • Curved or bowed outward like the outside of a bowl, circle, or sphere. 

  • having no internal angles greater than 180 degrees. 

  • having an epigraph that is a convex set. 

noun
  • A playing card made convex for use in cheating. 

  • A small convex mirror used to cheat by observing other players' cards. 

  • Any convex body or surface. 

sunken

adj
  • caused, by natural or unnatural means, to be depressed (lower than the surrounding area) or submerged 

  • Seeming to have fallen deeper back into the face due to tiredness, illness, or old age. 

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