catoptric

This term is a highly specialized technical adjective used almost exclusively in the fields of optics, astronomy, and physics. It describes systems that rely on reflection, specifically through the use of mirrors, to achieve their function. It is the direct counterpart to dioptric, which refers to the refraction of light through lenses.

Because of its narrow scientific application, the word is rarely encountered in general conversation. It carries a formal, academic register and is typically used to categorize types of telescopes or optical instruments, such as a catoptric telescope, where the primary light-gathering element is a mirror.