What is Diagram?

Legal Definition
A diagram is a symbolic representation of information according to some visualization technique. Diagrams have been used since ancient times, but became more prevalent during the Enlightenment. Sometimes, the technique uses a three-dimensional visualization which is then projected onto a two-dimensional surface. The word graph is sometimes used as a synonym for diagram.
-- Wikipedia
Legal Definition
1. a drawing that shows an idea or components and the relationships. 2. points kept that meet a condition or relation in an equation.