Editing Discrete mathematics (section)

===Set theory===
{{Main|Set theory}}
Set theory is the branch of mathematics that studies [[set (mathematics)|sets]], which are collections of objects, such as {blue, white, red} or the (infinite) set of all [[prime number]]s. [[Partially ordered set]]s and sets with other [[Relation (mathematics)|relations]] have applications in several areas.

In discrete mathematics, [[countable set]]s (including [[finite set]]s) are the main focus. The beginning of set theory as a branch of mathematics is usually marked by [[Georg Cantor]]'s work distinguishing between different kinds of [[infinite set]], motivated by the study of trigonometric series, and further development of the theory of infinite sets is outside the scope of discrete mathematics. Indeed, contemporary work in [[descriptive set theory]] makes extensive use of traditional continuous mathematics.