linear pair

two angles that are both adjacent and supplementary

conclusion

"then" part of a conditional statement

trapezoid

quadrilateral with exactly one pair of opposite sides parallel

decagon

10 sided polygon

inscribed

polygon whose vertices lie on the circle

octagon

8 sided polygon

perpendicular

two lines that meet to form right angles

theorem

statement that must be proven true

quadrilateral

4 sided polygon

angle bisector

segment that divides an angle into two congruent segments

rhombus

parallelogram with four congruent sides

postulate

statement assumed to be true

congruent

two polygons having the same shape and size

slope

ratio of rise over run

isosceles

triangle with two congruent sides

square

rectangle with four congruent sides

IFF

if and only if

median

segment from any vertex of a triangle to the midpoint of the opposite side

pentagon

5 sided polygon

rectangle

parallelogram with four right angles

parallelogram

quadrilateral with both pairs of opposite sides parallel

altitude

segment from the vertex of a triangle perpendicular to the line containing the opposite side

hypotenuse

longest side in a right triangle

coplanar

points that lie in the same plane

scalene

triangle with no congruent sides

obtuse

angle measure between 90 and 180

equilateral

triangle with all sides congruent

right

triangle containing one right angle

collinear

points that lie on the same line

CPCTC

corresponding parts of congruent triangles are congruent

similar

two polygons having the same shape

triangle

3 sided polygon

circumscribed

each side of a polygon is tangent to the circle

parallel

lines that lie in the same plane and do not intersect

tangent

a line that intersects a circle at exactly one point

diagonal

a segment joining two nonconsecutive vertices

hypothesis

the "if" part of a conditional statement

leg

sides of a right triangle

midpoint

a point in the middle of two points

adjacent

angles that have a common side and vertex

Supplementary

Angles that add to 180

complementary

angles that add to 90

acute

angle measure between 0 and 90