Axis of Symmetry
A straight line that separates a figure from its image by a reflection.
Therefore, a figure has an axis of symmetry if its two halves match when it is folded along this axis.
Property
Plane figures such as circles, squares, rectangles, isosceles triangles or isosceles trapezoids, equilateral triangles, regular polygons, etc., have at least one axis of symmetry. Squares have four axes of symmetry; rectangles and rhombuses have two, etc.
Example
