What is a Line Segment?
A line with a definite beginning and definite end
A line segment is a part of a line that has two fixed endpoints. Unlike a line, which goes on forever in both directions, a line segment starts and ends at specific points.
If you draw a straight path from point A to point B, that path is a line segment.
Line segments are often confused with lines and rays. Here’s how to tell them apart:
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A line has no beginning and no end. We put arrowheads on both ends to indicate the line goes forever in both directions.
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A line segment has a definite beginning and no end. A point indicates the beginning and an arrowhead indicates the line goes on forever.
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A ray starts at a point and goes on forever in one direction.
Line segments are often used to measure distances or define the sides of shapes like triangles, squares, and rectangles.
When Do Students Learn About Line Segments?
Students begin learning about line segments as part of their introduction to shapes and basic geometry.
Grades 1–2 – Recognizing Line Segments
Students learn to identify and draw line segments while exploring basic geometric shapes.
Grades 3–5 – Measuring and Using Line Segments
Students measure line segments, use rulers, and apply them to polygons and other geometry problems. In grade 4, they begin drawing line segments, including points, lines, and rays.
