A ray is a straight line that extends infinitely in one direction from a specific point, known as the origin. In geometry, it is often represented with an arrowhead to indicate its direction. Rays are commonly used in various fields, including mathematics and physics, to describe light paths and other linear phenomena. In the context of optics, rays are crucial for understanding how light travels and interacts with different surfaces. The concept of rays helps in the study of reflection and refraction, which are essential for designing lenses and other optical devices.