Line In geometry, lines are always straight. Lines are one-dimensional, and they go on forever in both directions. Line Segment Part of a line is called a line segment. Parallel Two lines are parallel if they never meet. Point A point is one location in space.
Points are zero-dimensional.
Back to Top Slope Slope is a number that shows how steeply a line slants. We often use the letter m to stand for a line's slope. Undefined In math, we call something undefined when we can't think of a description that makes sense. But zero multiplied by anything is zero, not six. Back to Top Vertical Vertical lines point straight up and down.