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.

Like

  • 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.

  1. Chapter 5 Class 9 Introduction to Euclid's Geometry
  2. Concept wise

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Davneet Singh
Davneet Singh is a graduate from Indian Institute of Technology, Kanpur. He has been teaching from the past 8 years. He provides courses for Maths and Science at Teachoo. You can check his NCERT Solutions from Class 6 to 12.