Definition:Conjugate Angles

The conjugate of an angle $$\theta$$ is the angle $$\phi$$ such that $$\theta + \phi = 2 \pi$$.

That is, it is the angle that makes the given angle equal to a full angle.

The angle $$2 \pi - \theta$$ is also known as the explement or explementary angle of (or for, or to) $$\theta$$.