Mirror lines: symmetry
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What you will learn
By the end, you can spot a line of symmetry and say how many lines of symmetry a shape or letter has.
Fold a butterfly picture down the middle and the two wings match exactly. That fold is a mirror line. When a shape has a mirror line, the two halves are the same but flipped — just like a reflection in a mirror.
Read the explanation
A line of symmetry is a fold line that splits a shape into two halves that match exactly when you fold along it. Some shapes have one line, some have several, and some have none. A square has four, a rectangle that is not a square has two, a circle has an endless number, and a scalene triangle has none.
- Fold along the mirror line: the halves must match exactly.
- A square has 4 lines of symmetry.
- A rectangle that is not a square has 2.
- Some shapes, like a scalene triangle, have none.