Division of two numbers is also called the ratio of two numbers. For example, 3: 2 is 3÷2, and it is recorded as 3: 2. Where ":"is a ratio symbol, which is pronounced as "ratio". The number before the ratio sign is called the former term of the ratio, and the number after the ratio sign is called the latter term. The quotient obtained by dividing the previous term of the ratio is called the ratio.

The concept of ratio comes from the comparison of multiple relationships between two similar quantities. In practical application, it is necessary to compare two different quantities, such as the ratio of distance to time. However, whether it is the ratio of similar quantity or different quantity, it can always be abstracted as the ratio of two numbers. By comparing two numbers, we can compare both the difference (difference ratio) and the multiple relationship (multiple ratio). In mathematics, ratio only compares the multiple relationship between two numbers. It should also be pointed out that the "ratio" used in sports competitions, although borrowed from ":",only indicates the record of the opposing sides, which is essentially different from the ratio in mathematics: (1) In mathematics, according to the definition of ratio, the latter term of ratio cannot be zero, but the score of sports competitions can be 2: 0, 0: 0, etc. (2) The ratio in mathematics can be simplified, but the score in sports competition cannot be simplified.