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## Chapter 6 Relations

## adjacency matrix

An adjacency matrix will show
Where the edges 'tween vertices go.
For a nice simple graph
You can cut through the chaff:
Noughts and ones in symmetrical flow.
psheil, The Omnificent English Dictionary In Limerick Form

One understands a set of objects completely only if the structure of that set is made clear by the interrelationships between its elements. For example, the individuals in a crowd can be compared by height, by age, or through any number of other criteria. In mathematics, such comparisons are called relations. The goal of this chapter is to develop the language, tools, and concepts of relations.