BitWithBite
Geometry · Quick Reference
Lines Cheat Sheet
In one line: a line extends infinitely in two directions with no curves or bends — one of the simplest yet most fundamental shapes in geometry.
Key Ideas
1Line. A straight path that extends infinitely in both directions, with no endpoints.
2Line Segment. A finite piece of a line with two definite endpoints, like the segment between points A and B.
3Ray. A part of a line with one endpoint that extends infinitely in only one direction.
4Parallel Lines. Two lines in the same plane that never intersect, no matter how far they extend, and always stay the same distance apart.
5Perpendicular Lines. Two lines that intersect at exactly a 90-degree angle.
Worked Examples
A path has one clear starting point but continues forever in one direction. What is this called?
A ray
Two lines meet at exactly 90 degrees. What are they called?
Perpendicular lines
Two railroad tracks run side by side, always the same distance apart, and never meet. What term describes them?
Parallel lines
Practice Yourself
Does a line have endpoints?
No, it extends infinitely in both directions
Does a ray have one endpoint or two?
One
Does a line segment have one endpoint or two?
Two
Do parallel lines ever intersect?
No