Certain curves are mathematical shapes that can be used to describe a variety of physical phenomena. The most common of these curves are sines, esses, and hips. Sines are smooth curves that repeat themselves in a wave-like pattern, and are often used to describe sound waves or light waves. Esses are curves that look like the letter 'S' and are used to describe the motion of objects in physics. Hips are curves that look like the letter 'H' and are used to describe the motion of particles in chemistry.