Lines and Angles

Basics of Geometry

Do you want to know what Geometry is? This word is actually derived from the Greek word ‘geometron’. Now, ‘geometron’ is actually made of two words – Geo and Metron. So geometry is the mathematical study of all shapes and figures. It can be seen everywhere in our everyday life. We live in a world of shapes and here we shall see how mathematics helps us understand the basics of geometry. Let us study this topic in detail.

Suggested Videos

previous arrow
next arrow
previous arrownext arrow


Basics of Geometry

Let us see some basics concepts of geometry. Let start it right away with the general terms frequently used in the basics of geometry.

Browse more Topics under Lines And Angles

You can download Lines and Angles Cheat Sheet by clicking on the download button below

Basics of Geometry

What is a Point?

A point is an exact location on the plane. It has no size. It is denoted by the capital letter of the English alphabet.

Collinear and Non- Collinear Points

Points which lie on the same straight line are collinear points. The points which don’t lie on the same straight line are non-collinear points.


Now we will discuss what is meant by a ray.  What comes to your mind when you think of the ray? Sun rays right? We know that the sun rays start from the sun and goes on endlessly. That means it has the starting point but it has no endpoint. So this nothing but a  ray.

Basics of Geometry

                                                                                                                                                 [Source: Shmoop]

The above figure shows what a ray is. A ray is nothing but a portion of a line. As the ray goes on endlessly, we cannot locate its end point. Let us name one of point as E. For the next point, we will just locate a point on the ray, say point F. So the name of the ray is ray EF.


A line is a straight path that is endless in both directions. That means it extends in both directions without end.

Line Segment

A line segment is a part of a line. The main difference the line and the line segment is that lines do not have endpoints while line segments have endpoints.


The plane is a two-dimensional surface. A plane has length and width, but no height, and extends infinitely far on all sides. It is made up of made up of an infinite amount of lines.


A midpoint of the segment is the point that divides the segments into two congruent segments.


Basics of Geometry

Angle is the combination of two rays with a common endpoint. The symbol for an angle is ∠. The corner point of an angle is called the vertex of an angle.  The two straight sides of the angle are the arms of the angle.

Parallel lines

Basics of Geometry

When the distance between a pair of lines is always the same, then we call such lines as parallel lines.

Intersecting Lines

Lines that intersect each other at one point are something we call as intersecting lines.

You can find our detailed article on Geometry here.

Solved Examples for You

Question 1: If line l, m and n are such that l || m and m || n, then:

Basics of Geometry

  1. l || m
  2. line l ⊥ n
  3. l and n are intersecting
  4.  line l = n

Answer : The correct option is A. Lines m and n are parallel to each other and hence they are making an angle of 0° between them. In the same way, m and n are parallel to each other and they are making an angle of 0° between them. Therefore, angles between lines l and n is also  0° which proves l || n.

Question 2: An angle which measures 180° is called:

  1. Zero
  2. Right
  3. Straight
  4. acute

Answer : The correct option is C. An angle whose measure is exactly 180° is a straight line.

Question 3: What are the basic concepts of geometry?

Answer: The basic geometrical concepts are dependent on three basic concepts. They are the point, line and plane. We cannot precisely define the terms. But, it refers to the mark of the position and has an accurate location.

Question 4: What is geometric math?

Answer: Geometry refers to a branch of mathematics which is focused on the measurement and relationship of lines, angles, surfaces, solids and points. For instance, the calculation of a triangle’s angles is an example of geometry.

Question 5: What is geometric mean?

Answer: In mathematics, the geometric mean refers to a mean or average that denotes the central tendency or typical value of a set of numbers by making use of the product of their values. This is opposite to the arithmetic mean which is making use of their sum.

Question 6: Who created geometry?

Answer: Euclid of Alexandria invented geometry. It is said he was possibly a student at the Academy by Plato. He was the one who wrote a treatise in 13 books (chapters), which he named The Elements of Geometry. Thus, in here, he presented geometry in an ideal axiomatic form, which we now know as Euclidean geometry.

Share with friends

Customize your course in 30 seconds

Which class are you in?
Get ready for all-new Live Classes!
Now learn Live with India's best teachers. Join courses with the best schedule and enjoy fun and interactive classes.
Ashhar Firdausi
IIT Roorkee
Dr. Nazma Shaik
Gaurav Tiwari
Get Started

Leave a Reply

Your email address will not be published. Required fields are marked *

Download the App

Watch lectures, practise questions and take tests on the go.

Customize your course in 30 seconds

No thanks.