At present, many people's understanding of "Bi" still stays in "the division relationship between two units with the same amount", in authoritative tools such as Ci Hai and Modern Chinese Dictionary.

The definition of "ratio" is also a mathematical term, indicating the multiple relationship between two similar quantities. Traditional mathematics textbooks also emphasize that the ratio of multiple relations cannot be expressed in units. Since "ratio" refers to the ratio of two quantities, it is easy for students to understand.

However, since the new curriculum reform, under the guidance of the spirit of curriculum standards, all versions of primary school mathematics textbooks have enriched the types of "ratio" into two types: one is the ratio between two similar quantities, and the other is the ratio between two different categories.

Textbooks such as Beijing Normal University Edition, People's Education Edition and Jiangsu Education Edition all introduce the ratio between similar quantities first, and then introduce the ratio between different types of quantities, such as "distance vs time". The three versions of the teacher's manual also distinguish and emphasize the two types. Among them, the teacher's book of People's Education Edition also explains the reasons for the change in detail.

From this point of view, the traditional textbooks stipulate that the ratio has no unit, and there are specific situations, that is, the ratio only indicates the multiple relationship between two similar quantities; Now the proportion of different categories has been added in the new textbook, and the meaning of proportion has changed. It represents a new quantity with practical significance. The author believes that units should be introduced in this case.