scheme vs undirected graph

scheme

noun
  • A chart or diagram of a system or object. 

  • A council housing estate. 

  • A systematic plan of future action. 

  • An orderly combination of related parts. 

  • A plot or secret, devious plan. 

  • A mathematical structure that enlarges the notion of algebraic variety in several ways, such as taking account of multiplicities and allowing "varieties" defined over any commutative ring (e.g. Fermat curves over the integers). 

  • Part of a uniform resource identifier indicating the protocol or other purpose, such as http: or news:. 

  • A representation of the aspects of the celestial bodies for any moment or at a given event. 

  • A portfolio of pension plans with related benefits comprising multiple independent members. 

verb
  • To plot, or contrive a plan. 

  • To plan; to contrive. 

undirected graph

noun
  • A graph in which the edges are not ordered, so the edge (a, b) is identical to the edge (b, a). 

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