Line segment

Here you will learn about a line segment, including what it is and how to identify it.

Students will first learn about a line segment as part of geometry in 4 th grade.

What is a line segment?

A line segment is part of a line – it has one end point and the other end goes on forever.

They can be shown on their own.

For example,

Line Segment image 1 US

They can also be shown within the line.

For example,

Line Segment image 2 US

Line segments are seen in many common 2D shapes and make up all sides of polygons.

For example,

Each side of a square is made up of line segments – parts of straight lines.

Line Segment image 3 US

There are also many examples of line segments in real life.

For example,

A side of a ruler is straight and has clear endpoints. It can be represented with a line segment.

Line Segment image 4 US

In all examples above, line segments can be used to measure. They are measured from one endpoint to the other. Sometimes the measurement is given.

If measuring yourself, just choose one endpoint as a starting point and measure to the other.

For example,

If line segment WZ is 7 \, cm, what are the lengths of the other sides of the square?

Line Segment image 5 US

Since all the sides of a square are line segments of the same length, they are also 7 \, cm.

What is a line segment?

What is a line segment?

[FREE] Lines Worksheet (Grade 4)

[FREE] Lines Worksheet (Grade 4)

[FREE] Lines Worksheet (Grade 4)

Use this quiz to check your grade 4 students’ understanding of lines. 10+ questions with answers covering a range of 4th grade lines topics to identify areas of strength and support!

DOWNLOAD FREE
x
[FREE] Lines Worksheet (Grade 4)

[FREE] Lines Worksheet (Grade 4)

[FREE] Lines Worksheet (Grade 4)

Use this quiz to check your grade 4 students’ understanding of lines. 10+ questions with answers covering a range of 4th grade lines topics to identify areas of strength and support!

DOWNLOAD FREE

Common Core State Standards

How does this relate to 4 th grade math?

  • 4th Grade – Geometry (4.G.A.1)
    Draw points, lines, line segments, rays, angles (right, acute, obtuse), and perpendicular and parallel lines. Identify these in two-dimensional figures.

How to identify line segments

In order to identify line segments:

  1. Look for two endpoints.
  2. State the name of the line segment(s) using a pair of letters.

Line segment examples

Example 1: one dimensional

Is the figure a line segment?

Line Segment image 6 US

  1. Look for two endpoints.

The figure is a line, with arrows pointing in each direction going on forever. There are no endpoints shown.

The figure is not a line segment.

Example 2: one dimensional

Name a line segment shown.

Line Segment image 7 US

Look for two endpoints.

State the name of the line segment(s) using a pair of letters.

Example 3: line segments in a pentagon

How many line segments are in the pentagon?

Line Segment image 11 US

Look for two endpoints.

State the name of the line segment(s) using a pair of letters.

Example 4: lines in a rhombus

How many line segments are in the rhombus?

Line Segment image 13 US

Look for two endpoints

State the name of the line segment(s) using a pair of letters.

Example 5: lines in the real world

Find a line segment on the cereal box.

Line Segment image 15 US

Look for two endpoints.

State the name of the line segment(s) using a pair of letters.

Example 6: measuring with line segments

Given line segment BE, point R is the midpoint. BR measures 44 \, cm. What is the length of the line segment BE?

Line Segment image 18 US

Look for two endpoints.

State the name of the line segment(s) using a pair of letters.

Teaching tips for line segments

  • Give students plenty of opportunities to look for and identify line segments in a variety of places. Worksheets that have a mixture of 2D shapes or real world examples can be useful for this skill, along with physical 2D and 3D objects found in the classroom.

  • Encourage students to go beyond just rotely solving practice problems to also creating line segments or requiring them to explain why they classified a figure as a line segment.

Easy mistakes to make

  • Confusing lines and line segments
    Line segments have definite endpoints, whereas lines go on forever in opposite directions. This can be confusing, especially since it is impossible to draw a complete line, since they are never ending. This is why it is important to draw lines with arrows on each end and clearly label line segments with two points.

  • Thinking that line segments have to be vertical or horizontal
    Line segments, just like lines, can be any orientation. As long as a figure has two endpoints and is part of a line, it is a line segment.
    For example,
    All the figures below are line segments.

    Line Segment image 20 US

  • Thinking that line segments have to be a certain length
    As long as a figure has two endpoints and is part of a line, it is a line segment, no matter how short or long.
    For example,
    The dime and the sailboat both have line segments.

    Line Segment image 21 US

Practice line segment questions

1. Which figure shows line segment AB?

Line Segment image 22 US

GCSE Quiz True

Line Segment image 23 US

GCSE Quiz False

Line Segment image 24 US

GCSE Quiz False

Line Segment image 25 US

GCSE Quiz False

Line Segment image 26 US

 

Based on the line segment definition, this figure has two clear endpoints. The points are connected by part of a straight line, so it is a line segment.

2. Does connecting points A and B form a line segment? Why or why not?

 

Line Segment image 27 US

No, because the ends of the line go on forever.

GCSE Quiz False

Yes, because the ends of the line go on forever.

GCSE Quiz False

No, because it is two points connected within a line.

GCSE Quiz False

Yes, because it is two points connected within a line.

GCSE Quiz True

Line Segment image 28 US

 

This figure has two clear endpoints. The points are connected by part of a straight line, so it is a line segment.

3. Which shape is made up of exactly 4 line segments?

Line Segment image 29 US

GCSE Quiz False

Line Segment image 30 US

GCSE Quiz False

Line Segment image 31 US

GCSE Quiz False

Line Segment image 32 US

GCSE Quiz True

Each vertex can be an endpoint. Let’s look at all the possibilities.

 

Line Segment image 33 US

 

Line Segment image 34 US

 

Line Segment image 35 US

 

Line Segment image 36 US

 

Each of the sides connected by the points is straight, which means they fall on a line.

 

The four sides of a trapezoid are 4 line segments.

4. Which shape has exactly 2 line segments?

Line Segment image 37 US

GCSE Quiz False

Line Segment image 38 US

GCSE Quiz False

Line Segment image 39 US

GCSE Quiz True

Line Segment image 40 US

GCSE Quiz False

Each vertex can be an endpoint. Let’s look at all the possibilities.

 

Line Segment image 41 US

 

This shape has 2 line segments. The curved part of the shape is NOT a line segment, since it is not part of a straight line.

5. Which real world shape (shown in blue) best represents a line segment?

Line Segment image 42 US

GCSE Quiz False

Line Segment image 43 US

GCSE Quiz True

Line Segment image 44 US

GCSE Quiz False

Line Segment image 43 US-1

GCSE Quiz False

The pointer of the compass is marked with clear endpoints that are connected within a straight line. The pointer of the compass represents a line segment.

6. Given line segment TB, point C is the midpoint. TB measures 34 \, inches. What is the length of the line segment TC?

 

Line Segment image 44 US-1

17 \, inches
GCSE Quiz True

64 \, inches
GCSE Quiz False

34 \, inches
GCSE Quiz False

12 \, inches
GCSE Quiz False

A midpoint divides a line segment into two equal parts. The length of a line segment can be divided by 2 to find the length of the line segment created by a midpoint: 34 \div 2=17.

 

Line Segment image 45 US

 

The length of line segment TC is 17 \, inches.

Line segment FAQs

How many points are there within a line segment?

While two points define the ends of the line segment, the part of the line within the line segment is made up of a collection of points. Since rational numbers can be infinitely small, there are an infinite number of points on any given line segment.

What is the distance formula?

When measuring line segments on a coordinate plane, the distance formula calculates the total distance of the line segment (between the two points).

The next lessons are

Still stuck?

At Third Space Learning, we specialize in helping teachers and school leaders to provide personalized math support for more of their students through high-quality, online one-on-one math tutoring delivered by subject experts.

Each week, our tutors support thousands of students who are at risk of not meeting their grade-level expectations, and help accelerate their progress and boost their confidence.

One on one math tuition

Find out how we can help your students achieve success with our math tutoring programs.

x

[FREE] Common Core Practice Tests (Grades 3 to 6)

Prepare for math tests in your state with these Grade 3 to Grade 6 practice assessments for Common Core and state equivalents.

40 multiple choice questions and detailed answers to support test prep, created by US math experts covering a range of topics!

Download free