In geometry, what is a line segment?

A line segment is defined as a part of a line that has two distinct endpoints. This means that it is finite in length, unlike a line, which continues infinitely in both directions. Since it is bounded, it can be measured, and you can determine the distance between its endpoints.

In contrast, the other choices describe different geometric concepts. For example, a straight line extending infinitely in both directions refers to a complete line without endpoints. A curve that connects two points does not conform to the straightness criterion of a line segment, and a line with a constant width describes a different shape, such as a rectangle or a parallelogram, rather than a line segment itself. The attributes of a line segment make it a fundamental concept in geometry, particularly in understanding properties of shapes and figures.