Definition:Bilateral Symmetry

Definition

Let $F$ be a geometric figure.

Plane Figure

Let $F$ be a plane geometric figure.

Let there exist a reflection $R$ in an axis of reflection $AB$ such that $\map R F$ is a (reflectional) symmetry.

Then $F$ has (plane) bilateral symmetry about $AB$.

Solid Figure

Let $F$ be a solid geometric figure.

Let there exist a reflection $R$ in an plane of reflection $P$ such that $\map R F$ is a (reflectional) symmetry.

Then $F$ has (solid) bilateral symmetry about $AB$.

Also see

• Results about bilateral symmetry can be found here.

Linguistic Note

The word bilateral derives from the Latin bis (meaning ‎twice) and laterālis (meaning pertaining to the side).

It literally translates as two-sided.

Sources

• 1986: David Wells: Curious and Interesting Numbers ... (previous) ... (next): $2$
• 1997: David Wells: Curious and Interesting Numbers (2nd ed.) ... (previous) ... (next): $2$
• 2008: David Nelson: The Penguin Dictionary of Mathematics (4th ed.) ... (previous) ... (next): bilateral symmetry