The relationship between elements and sets can be divided into "attribution" and "non-attribution". Belonging to: the symbol is "∈", for example, if a = {1, 2}, then 1∈A, 2 ∈ A. Not belonging to: the symbol is "_", for example, if a = {1,

In modern mathematics set theory, elements are every object that constitutes a set.

A collection consists of elements, and each object that makes up the collection is also called an element.

Set is one of the basic concepts in mathematics. The sum of things with certain attributes is called a set, and elements are everything that constitutes a set. The branch of mathematics that studies set operations and their properties is called set theory or set theory. The definition of set is very broad, not limited to mathematics, but also widely used in production and life. All things with specific attributes that make up a specific set can be called elements, so the definition of elements is also very broad.