How can we help?

You can also find more resources in our Help Center.

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

Right Angle

90 degree angle

Triangle

3-sided polygon

Acute Triangle

3-sided polygon, each angle is less than 90 degrees

Obtuse triangle

3-sided polygon, 1 angle greater than 90 degrees

Right Triangle

3-sided polygon. One 90 degree angle.

Isosceles Triangle

3-sided polygon. 2 congruent sides.

Equilateral Triangle

3-sided polygon. 3 congruent sides. 3 60 degree angles.

Scalene Triangle

3-sided polygon. No congruent sides

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-sided polygon with all congruent sides

segment

section of a line between two endpoints

vertex or vericies

the point where 2 lines meet

polygon

many-sided figure, closed, straight line segment

regular polygon

polygon with congruent sides and congruent angles

irregular polygon

polygon without all congruent sides

straight angle

angle measuring 180 degrees

complementary angles

angles whose sum equals 90 degrees

Supplementary angles

angles whose sum equals 180 degrees

regular polygon

a polygon with congruent sides and congruent angles

pentagon

5-sided polygon

hexagon

6-sided polygon

heptagon

7-sided polygon

octagon

8-sided polygon

nonagon

9-sided polygon

acute angle

an angle less than 90 degrees

obtuse angle

an angle more than 90 degrees

intersecting lines

lines that cross

perpendicular lines

lines that intersect and form 90 degree angles where they cross

angle

two rays that start from the same endpoint