Definition:Chord of Contact/Circle

Definition
Let $\CC$ be a circle embedded in the plane.

Let $P$ be a point also embedded in the plane which is outside the boundary of $\CC$.

Let $\TT_1$ and $\TT_2$ be a tangents to $\CC$ passing through $P$.

Let:
 * $\TT_1$ touch $\CC$ at $U$
 * $\TT_2$ touch $\CC$ at $V$.

$UV$ is known as the chord of contact on $\CC$ with respect to $P$.

Also see

 * Equation of Chord of Contact on Circle Centered at Origin, demonstrating that $UV$ is the polar of $P$ withy respect to $\CC$.