Perimeter: The distance around a two-dimensional shape.

Area: The size of a surface.

Volume: The amount of 3-dimensional space something takes up. 

Scale Factor: A scale factor is when you enlarge a shape and each side is multiplied by the same number. This number is called the scale factor.  

Similar triangles: Two triangles are similar if the only difference is size. 

Prism: A solid object with identical cross section all along its length. 

Cross section: A cross section is the shape made by cutting straight across an object. 

Sphere: A 3-dimensional object shaped like a ball.