Euclid listed some definitions.
Some of them are
- A point is that which has no part.
- A line is breadthless length.
- The ends of a line are points.
- A straight line is a line which lies evenly with the points on itself.
- A surface is that which has length and breadth only.
- The edges of a surface are lines.
is a surface which lies evenly with the straight lines on itself.
We observe that in the definitions,
some things need to be explained further.
- In Definition 2 - “A line is breadthless length.” , what is a length? What is breadthless?
In this question , we try to define some terms like parallel lines, radius of circle, square etc.