The term 'RELATING TO SIGHT' can be described by three words: OPTICAL (7 letters), OPTIC (5 letters), and VISUAL (6 letters). OPTICAL refers to the science of light and vision, including the properties of lenses and the eye. OPTIC is related to the sense of sight, and is often used to describe the eye or a lens. VISUAL relates to the perception of things with the eyes, such as the ability to see colors and shapes. All three terms are related to the sense of sight and the ability to see.