acute angle

angles that measures less than 90 degrees

right angle

angle that measures exactly 90 degrees

obtuse angle

angle that measures more than 90 degrees, but less than 180 degrees

straight angle

angle that measures exactly 180 degrees

complementary angles

sum of the measure of two angles is 90 degrees

supplementary angles

sum of the measure of two angles is 180 degrees

vertical angles

opposite angles formed by two intersecting lines

perpendicular lines

two intersecting lines that form 90 degree angles

parallel lines

lines that never intersect

skew lines

do not intersect and not parallel - they are in different planes

adjacent angles

formed by two intersecting lines, angles that are next to each other

transversal

line that intersects two or more lines

corresponding angles

on the same side of the transversal and are both above (or both below) the parallel lines