Euclid’s Definitions

Euclid listed some definitions.

Some of them are

  1. A point is that which has no part.
  2. A line is breadthless length.
  3. The ends of a line are points.
  4. A straight line is a line which lies evenly with the points on itself.
  5. A surface is that which has length and breadth only.
  6. The edges of a surface are lines.
  7. A plane surface 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.

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Davneet Singh

Davneet Singh has done his B.Tech from Indian Institute of Technology, Kanpur. He has been teaching from the past 14 years. He provides courses for Maths, Science, Social Science, Physics, Chemistry, Computer Science at Teachoo.