Class 9 Maths Euclid Geometry | Undefined Terms |

**Undefined Terms:**

If you see these 100 definitions, Euclid has used terms like part, length, breadth etc without defining it. E.g A point is that which has no **part**. Here part is not defined.

Even if we define Part as something that occupied area, again we have to define new term; in this case it is area. To define, many things have to be defined & the chain is endless. Thus mathematicians agreed to leave some geometric terms as undefined. However we do have intuitive feeling for the geometric concepts f point with the definition provided by Euclid. So we represent point as a dot, even though dot has some dimension. Similar issues were there with terms length & breadth & thus these terms were not defined as well. Thus we take **point, line & plane** as undefined terms.

- A point is that which has no
**part**. - A line is
**breathless** - A
**surface**is that which has**length**and**breadth** - A plane surface is a
**surface**which lies evenly with the straight lines on itself.

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