Point is not something new to us. Many graphs are being drawn using points.

A point is smaller than a tip of a pencil or pen used by us. Therefore a point has not length, width, height or thickness.

A point indicates a definite position.

Points are usually denoted by capital letters A, B, C and so on as given below.

Observe the figure given below carefully.

As the space in between the points decreases they join to form a line. A line is a set of points closely arranged without gap.

Mark A, B on a sheet of paper using a scale and draw a line passing through these points.

This is a straight line.

It is represented as straight line AB or line "l".

When we represent a straight line as AB, it means,

(i) The line passes through the points A and B.

(ii) The line extends on either side of A and B.

Observe the names given for the following straight lines.

A ray starts from a fixed point and extends indefinitely in other direction.

1. Starting point of the ray is A.

2. The ray passes through the points A and B.

3. The ray extends through the point B.

A ray is a straight line with a starting point and extends indefinitely in one direction.

If a sheet of paper is folded and then opened, the folded part represents the line segment.

It is shown in the figure given below.

Mark X, Y and Z on the straight line AB.

Consider AX a part of the straight line, which starts at A and ends at X. So, it has a particular length. This is called a line segment. It can be denoted as line segment AX.

Few more line segments from the above figure are AY, AB, XY, XB, YB, XZ.

Therefore line segment is a part of a line. It has a starting point and end point.

A line segment has definite length.

Straight lines, points and rays can be represented in a sheet of paper or on the black board. Isn't it ?

Likewise floor, wall, black board, card board and top portion of the table are few examples of plane.

A plane is a flat surface which extends indefinitely in all directions as given in the figure given below.

How many points are required to form a plane ?

It is enough to have three points that do not lie on the same straight line.

**Collinear Points :**

1. Draw the straight lines passing through the points A and B.

2. Check whether you can draw a straight line passing through the points A, B and C.

3. Draw a straight line passing through the points P, Q and R.

**Solution :**

1. You can draw a straight line passing through the two points A and B.

2. Since A, B and C are on the same straight line, a straight line can not be drawn through A, B and C.

3. A straight line can be drawn through P, Q and R, as they lie on the same straight line.

So, P, Q and R are collinear points.

Hence, the following statements are true.

(i) A straight line can be drawn through any two given points.

(ii) It is not always possible to draw a straight line passing through any 3 points.

(iii) But a straight line can be drawn passing through 3 collinear points.

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