Two-dimensional (2D) shapes are completely flat ... 2D shapes have sides and corners. Another name for a corner is a vertex. A vertex is a point where two or more lines meet.

Mathematicians’ Favorite Shapes Hold the Key to Big Mathematical Mysteries ...

Do you know what a circle looks like? Can you name some other shapes too? A two dimensional (2D) shape is made of lines. Sometimes the lines are curved and sometimes the lines are straight.