Symmetric – Identical parts facing each other. The simplest type is a mirror.
See metal tick (symmetric) with a mirror. (Mirrors always provide a symmetrical view in reflection.)
A circle is symmetrical through any line that divides it perfectly in half.
A rectangle is symmetrical about a vertical line through the centre, and a horizontal line through the centre.
This triangle is symmetrical about the vertical line passing through its centre.
This plane shape is symmetrical about the red line that passes through it.
Lines such as the ones above or those on a graph may also be symmetrical.