What is the area? The current primary school textbook defines it this way: "The size of the surface or closed plane figure of an object is called their area." (People's Education Press, Primary School Mathematics Room, 200 1, 654, 38+February edition, Mathematics, Volume VII, p. 92).

The author thinks that the concept of "plane figure" in the definition is limited by "plane", which makes its extension smaller and its inclusiveness lower. For example, for a country, its area is a figure with a certain size surrounded by the boundary line on the surface of the spherical object of the earth, but it is not a plane; A cylinder's side is "flat" only when it is unfolded, and its own state is curved. Therefore, the area "is used to measure the area on a plane or a curved surface" (see page 5302 of Ci Hai, Shanghai Dictionary Publishing House, 1989), which is not limited to "plane graphics".

In order to avoid limitation and ambiguity, I think the area can be simply defined as "the size of an object surface or an enclosed graphic surface, which is called their area." In this way, the concept of "face" is used before and after, so that the semantics are consistent and coordinated. More importantly, it is more logical to make the definition language truly reveal the essential attributes of things, because "mian" is a kind of "trace" with length, width and thickness (see Hubei Dictionary Publishing House and Sichuan Dictionary Publishing House, 1995), and this trace is not necessarily ".