Number is an abstract concept for counting, marking or measuring, and it is a simple symbolic record form for comparing the levels of things with the same attribute. Algebra is a branch of mathematics that studies the theory and method of algebraic operation of real numbers and complex numbers and polynomials with their coefficients.

Numbers include algebra, and numbers consist of algebra and geometry. Numbers refer to specific numbers, which are directly represented by numbers, such as 1, 2, 3. Algebra, on the other hand, uses letters to represent numbers. For example, A, B and C stand for 1, 2 and 3 respectively. Algebraic structure types include groups, rings, fields, modules, linear spaces and so on. Generally, the arithmetic operations of numbers are only addition, subtraction, multiplication and division.

There are real and imaginary numbers, and the imaginary number is expressed as I 2 =- 1. Real numbers are divided into rational numbers and irrational numbers. Irrational numbers are infinite acyclic decimals, such as √2 and π, while rational numbers can be expressed as fractions. There are three kinds of numbers in algebra: rational numbers, irrational numbers and complex numbers. Algebraic expressions include algebraic expressions, fractions and roots. The connection between number and algebra is that number consists of algebra and geometry.