Set theory: a basic branch of mathematics, whose research object is general set. Set theory or set theory is a mathematical theory to study a set (a whole composed of a bunch of abstract objects), including the most basic mathematical concepts such as set, element and subordinate relationship.

Graph theory: Graph theory is a branch of mathematics. It takes graphics as the research object. A graph in graph theory is a graph composed of several given points and lines connecting the two points. This kind of figure is usually used to describe a certain relationship between some things, with points representing things and lines connecting two points indicating that there is such a relationship between two corresponding things.

Discrete mathematics: Discrete mathematics is a mathematical discipline that studies the structure and relationship of discrete quantities, and it is an important branch of modern mathematics.

All three are branches of mathematics.