A mathematical diagram is a picture that is used to help you understand math. It looks kind of like a drawing but it shows you the relationship between different numbers and how they work together. For example, a multiplication diagram might show a bunch of circles with numbers inside. Each circle is multiplied by the number in the circle next to it, so you can see how the numbers change when you multiply them. Mathematical diagrams can help to make math easier to understand so it's fun and less confusing.