"Infinity" (also called "infinity") refers to infinity or infinity in number. In mathematics, ∞ is often used to mean "infinity", but it is not a symbol with precise definition. According to the research of mathematical historians, the symbol ∞ was originated by Wallis and first appeared in his book arithmetica infinitorum published by 1656. Newton once said that his first discovery of "flow calculus" (differential calculus) was inspired by Wallis' works.

Later, people often use the symbol ∞ to represent the infinite increase of a variable X, which is abbreviated as x-∞. This is very important. With this concept, infinitesimal is defined as the reciprocal of infinite variables. In this way, we can have limit theory and lay the foundation for calculus. This is the result of19th century mathematicians Cauchy and Wilstrass.

Cantor is a mathematician, who boldly founded the "infinite mathematical theory" in the late19th century. His main contributions are infinite set theory and super-finite number theory. According to him, there are three kinds of infinity, one is "absolute infinity" (also called metaphysical infinity), the other is "physical infinity" and the third is "mathematical infinity".

Finite means that there is a certain number after enumeration.