| A | B |
|---|
| Lines in the same plane that never intersect. | Parallel |
| Lines in the same plane that intersect at 90 degrees or right angles | Perpendicular |
| Lines that lie in different planes that are neither parallel nor intersecting | Skew |
| A triangle with all three angles less than 90 degrees | Acute |
| A triangle with one angle greater than 90 degrees | Obtuse |
| A triangle with one 90 degree angle | Right |
| A triangle with no congruent sides | Scalene |
| A triangle with at least two congruent sides | Isosceles |
| A triangle with three congruent sides | Equilateral |
| A closed plane figure with three sides | Triangle |
