Line vs Line Segment
A straight line is defined as one dimensional figure, with no thickness or curvatures and extending infinitely in both directions. It is more common to use ‘line’ than the ‘straight line’ in practice.
A line can be uniquely determined by two points lying on it. Therefore, it implies that there is one and only straight line between two given points. Because of that we can use two points to draw a straight line spanning from one point to another. Even though we call it a line, it actually is a line segment. More precisely, a line segment is a short piece of a straight line, where its starting point and end point are distinctively marked.
When drawing straight lines, two arrowheads pointing outwards are put on the ends, to indicate that it extends to infinity. But in case of line segments there are only the end points.
What is the difference between Line and Line Segment?
• The line is unending and extends to infinity. Therefore, it has no starting or end point. This is denoted in a drawing by the arrowheads put on the ends of the drawn line.
• The line segment is actually a smaller section of the line. Therefore, it has a starting point and an ending point.
• A line has no measurable length (its infinite), but the line segments have a finite length.
• In common usage, we use line segments not lines.