Symmetry is when an object has exactly similar parts facing each other.

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A plane figure is said to have "symmetry" if it can be folded along a line, so that the two parts match.

The line where the fold would occur is called the "line of symmetry."

Note 1: A plane figure, some times, may have two or more lines of symmetry.

Note 2: It is also possible that, some plane figures have no line of symmetry.