Lemniscate

A lemniscate is a figure-eight-shaped curve that is a type of algebraic curve. The most famous version is the lemniscate of Bernoulli, which can be described mathematically by the equation: \[ \left( x^2 + y^2 \right)^2 = a^2 (x^2 - y^2) \] where \( a \) is a constant that defines the size of the curve.