The main types of lines are horizontal lines, vertical lines, perpendicular lines and parallel lines. Other categories of lines include diagonal lines, curved lines, contour lines and continuous lines.
Five types of lines are typically used in geometry:
- Vertical lines run straight up and down and have an undefined slope.
- Horizontal lines run straight across and have a slope of zero.
- Perpendicular lines intersect each other at a 90-degree angle. They occur when horizontal and vertical lines meet.
- Parallel lines are two straight lines that never intersect.
- Skew lines are special lines that exist in three or more dimensions and are nonparallel lines that never intersect.
Two types of lines are typically used in drawing:
- A contour line is a single line that creates the outline of a figure and shows height and width.
- Continuous lines in drawing are created when an image is drawn using only one line.