A secant is a line that intersects a curve at two or more points. In the context of a circle, the secant line cuts through the circle, creating two points of intersection. This concept is important in geometry and trigonometry, where secants help in understanding the properties of circles and other shapes. In trigonometry, the secant function, denoted as sec, is the reciprocal of the cosine function. It is defined as the ratio of the length of the hypotenuse to the length of the adjacent side in a right triangle. The secant function is used in various applications, including calculus and physics.