You need to know the properties of the different types of triangle and square. Circles always have a radius, a diameter, and a circumference. You also need to know about other polygons such as hexagons and pentagons.
The perimeter is the length of the sides of a shape, and the area is the surface area that it covers. You need to know how to work out how many lines of symmetry a 2D shape has.
Triangles have three sides. There are many different types of triangles:
Quadrilaterals have four sides. Here are some special quadrilaterals:
Pentagons have 5 sides
Hexagons have 6 sides
Heptagons have 7 sides
Octagons have 8 sides