# Why do so many children's book confuse discs with circles? [duplicate]

The difference between a disc (disk) and a circle is crystal clear to me:

However, in many children's books, a disc is usually called a circle:

Why do many children's book confuse discs with circles? Should we teach children the difference between a disc and a circle?

• The underlying reason could probably be the dual meaning of circle in everyday English. Thus, confusion wouldn't be the best word to describe the situation. Commented Mar 25, 2022 at 15:41
• I see an annulus and a disk. Commented Mar 25, 2022 at 18:00
• This isn't "confusion", this is (appropriately) using one of the the ordinary English meanings of the word "circle" rather than the technical mathematical definition. Commented Mar 25, 2022 at 21:36
• Are you perhaps implying that the surface area of a circle is zero?
– knl
Commented Mar 25, 2022 at 23:18
• @JoelReyesNoche, you are right. The formula $\pi r^2$ gives the area of a disc, while the area of every circle is zero. Commented Mar 27, 2022 at 1:46