A tangent is a straight line that touches a curve at a single point without crossing it. In geometry, tangents are often discussed in relation to circles, where a tangent line meets the circle at exactly one point. This point is called the point of tangency. Tangents are important in various fields, including mathematics and physics, as they help describe the behavior of curves. In calculus, the concept of a tangent is extended to functions. The tangent line to a function at a specific point represents the instantaneous rate of change of the function at that point. This is closely related to the derivative, which is a fundamental concept in calculus that measures how a function changes as its input changes.