In trigonometry, the tangent is considered as one of the key trigonometric functions. It is defined as the ratio of the length of the opposite side to the length of the adjacent side of a right triangle. Let's consider a right triangle with an angle θ. The tangent of θ, denoted as tan(θ), is given by the formula: tan(θ) = opposite/adjacent.

To better understand this concept, let's take an example. Suppose we have a right triangle ABC, where ∠B is the right angle. If side AB is the adjacent side to angle θ and side BC is the opposite side, then the tangent of θ can be calculated as tan(θ) = BC/AB.

Tangent as a ratio allows us to relate the sides of a triangle to the measure of an angle without solely relying on actual measurements. This enables us to solve various angle and side length problems using trigonometry.