Circle of Apollonius
The Circle of Apollonius is defined as the locus of a point \(P\) which moves in such a way that the ratio of its distances from two fixed points, \(A\) and \(B\), is a constant \(\lambda\), with \(\lambda \neq 1\). This geometric construct is named after the ancient Greek geometer Apollonius of Perga, who extensively studied these circles among other conic sections.