# Points, Lines, Line Segments, & Rays

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Points, Lines, Line Segments, & Rays
CCSS.MATH.CONTENT.4.G.A.1

## Points, Lines, Line Segments & Rays – Definition

In this learning text we are going to talk about geometry. Geometry is the study of shapes, sizes, angles and dimensions of objects. To understand geometry, we must learn the key definitions, which you will use when learning geometry in different grades. They are: points, lines, line segments & rays.

• A point is a specific location on a flat surface.
• A line is a set of points that extends definitely or without ending in both directions. We often show this by putting an arrow at each end of lines we draw.
• A line segment is part of a line between two endpoints.
• A ray is part of a line that has an end point on one side but extends the other direction without ending.

Let’s look at some real-life examples to see how these concepts work.

## Points, Lines, Line Segments & Rays – Examples

Using a baseball field as visual representation, we are going to show points, lines, line segments & rays as real-life examples. For revision, have a look at the table below for an overview of points, lines, line segments and rays.

Term Explanation
point A point is a specific location on a flat surface.
line A line is a set of points that extends definitely
or without ending in both directions.
line segment A line segment is part of a line between two endpoints.
ray A ray is part of a line that has an end point on one
side but extends the other direction without ending.

Now let’s look at the points on the baseball field: they can represent players on the field. Remember points are created by marking specific locations on a flat surface. Below you can see a baseball diamond with different points. The bases make points, the home plate is a point and the pitching mound is a point too. The points around the field are representing the players. This is just one example to visualize the concept of a point.

Let’s look at examples of lines. A line is created by connecting specific points. The green lines below are never-ending lines because they have the ability to continue forever in both directions. In the picture below we can only see a portion of a line as the line never ends.

In mathematics, we put an arrow at the end of a line which indicates the direction of a never-ending line.

A Line segment is just a small portion or section of a line. We mark the section of a line with endpoints to indicate we are looking at this small part.

On this baseball field, there are many line segments: The joined lines between the bases and home plate are line segments. Each connection from one point to another is a line segment. The line from the pitcher’s plate to the home plate is also a line segment, even the ball thrown from third base to first base will make a line segment.

The line segments can be anywhere, all depending on the position or points where the player is standing.

In a baseball field, a ray can be created when the player is in the batter’s box. The home plate is the position of the end point, and the lines are extended with no endpoints.

As mentioned before, the baseball field is just one of the real-life examples showing points, lines, line segments & rays.

## Points, Lines, Line Segments & Rays – Summary

All geometry is based on these concepts:

• A point is a specific location on a flat surface.
• A line is a set of points that extends definitely or without ending in both directions. We often show this by putting an arrow at each end of lines we draw.
• A line segment is part of a line between two endpoints.
• A ray is part of a line that has an end point on one side but extends the other direction without ending.

This text explored the meaning of the terms points, lines, line segments and rays. If you need more information, watch the video and complete the worksheet related to points, lines, line segments & rays.

What is a point?
What is a line?
What is a line segment?
What is a ray?

### TranscriptPoints, Lines, Line Segments, & Rays

Nico and Nia are trying out for the Geo City Giants. [Coach:] “Today, we hope to have some new members join our team.” [Coach:] “FIRST, We are going to go over some of the fundamentals so LISTEN UP!” Before Nico and Nia can try out for the team, Coach needs to explain, Points, Lines, Line Segments, and Rays. Geometry is the study of shapes, sizes, angles, and dimensions of objects. In order to understand geometry, we need to learn the fundamentals. All geometry is based on these beginning concepts: A POINT is a specific location on a flat surface. A LINE is a set of points that extends indefinitely, or without ending, in BOTH directions. We often show this by putting an arrow at each end of the lines that we draw. A LINE SEGMENT is part of a line between two endpoints. A RAY is part of a line that has an endpoint on one side but extends in the other direction without ending. Using the baseball field as our example, let’s see how these concepts, or ideas, work in everyday life. Points are created by marking specific locations on a flat surface. What points do you see on the baseball diamond? The bases make points, home plate is a point, and the pitcher’s mound is also a point on the field. We can even create more points on the field when we put the players in their positions.

A line is created by connecting a set of points. Look at the foul lines. We say that lines are indefinite, or never-ending because they have the ABILITY to continue forever(...) in both directions. We are only seeing a portion of the line. This end could keep on going, indefinitely, in this direction. When we look at only a section of a line, we call it a LINE SEGMENT. We mark the section of the line with endpoints, to indicate we are only looking at this part. In baseball, there are many line segments. The paths between the points made by the bases are line segments, and from the pitcher’s mound to home plate is a line segment. Even when the third baseman, throws to the first baseman, a line segment is made. Do you see more line segments on the field? Yes, line segments can be anywhere depending on the position, or points, of the players. In baseball, a ray can be created when a player is at-bat. Homeplate is the position of the endpoint… and the lines would extend outward like this. Baseball is one example of how we use geometry in everyday life. While Nico steps up to the plate, let's review. Remember… All geometry is based on these beginning concepts: A POINT is a specific location on a flat surface. A LINE is a set of points that extends indefinitely in BOTH directions. A LINE SEGMENT is part of a line between two endpoints. A RAY is part of a line that has an endpoint on one side but extends in the other direction without ending. "[Coach:] “NICO, you’re up, “Let’s see what ya got!”

## Points, Lines, Line Segments, & Rays exercise

Would you like to apply the knowledge you’ve learned? You can review and practice it with the tasks for the video Points, Lines, Line Segments, & Rays .
• ### What is geometry?

Hints

What do the words point, lines, line segments, and rays relate to?

Think about the size of something.

Solution

The correct answer is studying the shapes and sizes of an object. Geometry is all about defining a shape. We do that by looking at different elements that create a shape such as points, lines, line segments, and rays.

• ### What do these geometry terms mean?

Hints

This is an example of a ray.

Solution

A point is a specific location on a flat surface. In the image, the point is pink.

A line is a set of points that extends without ending. In the image, the lines are blue.

A ray is part of a line that has one endpoint. In the image the rays are yellow.

A line segment is part of a line between two endpoints. In the image, the line segments are green.

• ### Identify real world objects that have been created using geometry

Hints

Remember geometry is the study of shapes, sizes, angles, and dimensions of an object

A road doesn't go on forever, but it feels like it does.

People use dots to mark cities or locations on a map.

Have you ever heard the phrase, "the sun's rays are beaming down on us?"

Solution

The correct pairs are:

• ray and sun; because the sun's rays only extend in one direction
• point and map; the red locations on the map are locations that take up an area
• line segment and pencil; the point of the pencil is one end and the eraser is the other end. A pencil does not extend forever.

• ### How many points are in the object?

Hints

Corners are created when line segments come together.

Lines, line segments, and rays are made up of many points. In a shape, the point where two line segments intersect is called a corner.

Solution

There are 9 corners altogether in the image.

A rectangle is made up of 4 line segments, so there will be 4 corners where the line segments come together for both rectangles.

A triangle is only made up of 3 line segments, so there are only 3 corners on a triangle

To find the total number of corners, you just count all the dots you see in the object. Be careful not to count them twice!

• ### Identify examples of lines.

Hints

A line extends in two directions.

A line is created by connecting a set of points.

Lines are never ending.

Solution

The number line is an example of a line because numbers extend indefinitely in both directions.

Lines a and b are parallel lines. These are lines that extend indefinitely in both directions but never cross each other.

• ### Identify examples of geometric terms.

Hints

A line goes on indefinitely but a line segment is only part of a line.

Lines, line segments, and rays do not curve.

Solution

Here we can see:

• the lines are blue
• the rays are yellow
• the points are pink
• the line segments are green.
The oval is a solid shape, so it is not a line, ray, point, or line segment.

Lines, rays, points, and line segments do not curve, so they should not be highlighted either.