In geometry, it's a common mistake to say a segment and a line are one and the same.

A segment has a definite beginning and a definite end, with each end represented by a point.

Examples of segments include the length of a table, the distance of a straight road, etc.

On the other hand, a line has no definite beginning or end.

A segment is part of a line, but a line is not part of a segment.

We can see so many straight-line examples around us, edges of a building, roads we use to travel.