Triangles
A shape straight sides, and encloses one area
Polygon
A polygon with four sides
Quadrilateral
A small angle, less than 90°
Acute angle
A polygon with three sides and three angles
Triangle
A polygon with five sides
Pentagon
A 90° angle it looks like a L
Right angle
A triangle with three acute angles
Acute angled triangle
A polygon with six sides
Hexagon
180 degrees and looks like a straight line
linear angle
A triangle with one obtuse angle
Obtuse angled triangle
A polygon with seven sides
Heptagon
More than 180°, but less than a whole angle or 360°
Reflex angle
A triangle with one right angle
Right angled triangle
A polygon with nine sides
Nonagon
Whole circle or 360°
Whole angle