What makes a shape symmetrical?
A 2D shape is symmetrical if a line can be drawn through it and either side is a reflection of the other.
The line is called a line of symmetry.
This is sometimes called a 'mirror line' or 'mirror symmetry', because if you put a mirror on the line, the reflection would show the whole shape.
• An isosceles triangle has 1 line of symmetry.
• A square has 4 lines of symmetry.
• A circle has unlimited lines of symmetry!