Real number is a general term for rational number and irrational number. Mathematically, real numbers are defined as the number of corresponding points on the number axis. Real numbers can be intuitively regarded as finite decimals and infinite decimals, and can "fill" the number axis. But the whole of real numbers can't be described only by enumeration. Real and imaginary numbers * * * make up a complex number.

Real numbers can be used to measure continuous quantities. Theoretically, any real number can be expressed as an infinite decimal, and to the right of the decimal point is an infinite series (cyclic or acyclic). In practice, real numbers are often approximate to a finite decimal (n digits are reserved after the decimal point, and n is a positive integer, including integers). In the computer field, because computers can only store a limited number of decimal places, real numbers are often represented by floating-point numbers.