Shapes are often defined, or named, by how many sides they have.
Let's learn about the most common shapes.
A circle is made up of a curved side. It has no straight sides.
A triangle is made of 3 straight sides.
There are three types of triangles.
A triangle with all sides equal in length is called an equilateral triangle.
The second triangle, has only two equal sides.
A triangle with only two equal sides is called an isosceles triangle.
The third triangle has no equal sides.
A triangle with no equal sides is called a scalene triangle.
Polygons with 4 straight sides are called quadrilaterals.
Tip: The prefix "quad" means four.
There are a bunch of different quadrilaterals.
Parallelograms are quadrilaterals with two pairs of parallel sides.
Parallel lines never intersect. They go in the same direction and never meet.
Tip: we often use little arrows like > on lines to show they're parallel.
Rectangles are parallelograms where the sides meet at perpendicular angles.
Tip: Think of perpendicular lines as the opposite of parallel lines.
Perpendicular lines intersect, or cross, at 90 degree angles, also called right angles.
A square is a rectangle with 4 equal perpendicular sides.
A rhombus is a quadrilateral with 4 equal sides, but the angles can be big or small.
All squares are rhombi (the plural of rhombus), but not all rhombi are squares.
Tip: think of a rhombus like a smooshed square.
A square is a rhombus with only 90 degree angles.
A trapezoid is a quadrilateral with at least one pair of sides being parallel.
Only one pair of opposite sides is parallel in this trapezoid 👆.
Every parallelogram is also a trapezoid, since every parallelogram has two pairs of parallel sides, and trapezoids all have at least one pair of parallel sides.
A kite is a quadrilateral with two adjacent lines that are of equal length.
The two longer sides at the bottom are also equal.
A polygon with 5 sides is called a pentagon.
A hexagon has 6 sides.
A shape with 7 sides is called a heptagon.
An octagon is a shape with 8 sides.
Great job learning how to classify shapes based on lines.
Now, try the practice to help you remember for longer, and get better grades too.