A Venn diagram is a diagram that shows all possible logical relations between a finite collection of sets. It is the intersection of two or more circles, each representing one set, that are placed together in such a way as to show all the possible logical combinations of their memberships. The shapes of the circles can vary, but they need not be round, nor do they need to touch one another. The shapes may represent actual physical objects (e.g., countries) or more abstract concepts (e.g., colors).