isosceles triangle

a triangle with two equal sides

vertex

The common endpoint of an angle

obtuse triangle

a triangle with one obtuse angle

right triangle

a triangle with one right angle

scalene triangle

a triangle with no two sides of equal length

equilateral triangle

a triangle with three equal sides

straight angle

an angle that measures 180 degrees

obtuse angle

An angle more than 90 degrees

right angle

an angle that measures 90 degrees

angle

two rays with a common endpoint

acute angle

An angle less than 90 degrees

plane

An endless flat surface

line segment

part of a line with two endpoints

point

An exact location in space

intersecting lines

lines that cross at one point

ray

Part of a line that has one endpoint and extends forever in one direction.

line

A straight path of points that goes on forever in two directions

perpendicular lines

Two lines that intersect to form right angles

parallel lines

Lines in the same plane that do not intersect

Skew lines

Lines that do not intersect, are not parallel, and are not in the same plane