The ratio between the lengths of the adjacent side and the opposite side in a right triangle for a specific angle, $\theta ,$ is called the cotangent of $\theta$ and is written as $\cot (\theta ).$

The ratio is always the same for any given angle. If the adjacent side is, for example, twice as long as the opposite side, the ratio is $\cot (\theta )=\frac{2}{1}.$ This quotient holds true because the triangles are bound by similarity. Cotangent only states the ratio between the adjacent side and the opposite side, it gives no indication about the lengths of the individual sides.