# Definition:Line/Straight Line Segment

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## Definition

A **straight line segment** is a line segment which is straight.

In the words of Euclid:

*A***straight line segment**can be drawn joining any two points.

(*The Elements*: Book $\text{I}$: Postulates: Euclid's First Postulate)

Thus a definition for **straight line** which is frequently encountered is:

*A***straight line**is the shortest distance between two points.

This is all very well but it assumes that the line in question terminates at two particular endpoints.

## Also known as

In their definition of a **straight line segment**, some sources take straightness for granted, and refer to such as just a **line segment**.

Some sources refer to just a **segment**, but that term has multiple meanings.

## Sources

- 1947: William H. McCrea:
*Analytical Geometry of Three Dimensions*(2nd ed.) ... (previous) ... (next): Chapter $\text {I}$: Coordinate System: Directions: $\S 1$. Introductory: Nomenclature - 1998: David Nelson:
*The Penguin Dictionary of Mathematics*(2nd ed.) ... (previous) ... (next):**line segment** - 2008: David Nelson:
*The Penguin Dictionary of Mathematics*(4th ed.) ... (previous) ... (next):**line segment** - 2014: Christopher Clapham and James Nicholson:
*The Concise Oxford Dictionary of Mathematics*(5th ed.) ... (previous) ... (next):**line segment**