convex vs sigmoid

convex

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

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

  • 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. 

sigmoid

adj
  • Curved in two directions, like the letter "S", or the Greek ς (sigma); having a serpentine shape. 

  • Relating to the sigmoid colon. 

  • Exhibiting logistic growth; having a graph that accelerates until it reaches a carrying capacity. 

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