square

4 equal sides. 90 degree angles.

rectangle

quadrilateral. 90 degree angles.

quadrilateral

4-sided polygon

perimeter

distance around a figure

area

number of square units it takes to cover a figure

base

bottom of a figure

right angle

90 degree angle

triangle

3-sided polygon

acute triangle

Type of Triangle when each angle is less than 90 degrees

obtuse triangle

Type of Triangle (angle) when 1 angle greater than 90 degrees

right triangle

Type of Triangle with one 90 degree angle.

isosceles triangle

Type of Triangle with 2 congruent sides.

equilateral triangle

Type of Triangle with 3 congruent sides.

scalene triangle

Type of triangle with no congruent sides

hypotenuse

side opposite the right angle in a right triangle

parallelogram

4-sided quadrilateral. 2 pairs of parallel lines

parallel lines

lines that will never intersect

trapezoid

4-sided quadrilateral. 1 pair of parallel lines

congruent

same size, same shape

rhombus

4 equal-sided polygon

segment

line between two points

polygon

many-sided figure, closed, straight line segment

complementary

two angles whose sum equals 90 degrees

supplementary

two angles whose sum equals 180 degrees

perpendicular lines

A set of lines that intersect at 90 degrees

parallel lines

A set of lines that are equal distance apart and will never intersect no matter how far they are extended; railroad tracks

intersecting lines

lines that cross at an angle that is NOT 90 degrees

line segement

has a definite starting point and definite ending point; a ruler

line

extends in each directions infinitely; space

ray

has a definite starting point and an infinite line; the sun's rays

straight line

has 180 degrees

acute angle

an angle that measures less than 90 degrees

obtuse angle

an angle that measures more than 90 degrees