n pl but sing in constr 1 : a branch of optics dealing with the refraction of light esp. by lenses 2 : refractive optics esp. of a lens or system of lenses <correction of refractive error of the peripheral of the eye -Anne Lamont et al> .
Similar sounding terms: Dip·ter·yx
Published under license with Merriam-Webster, Incorporated. © 1997-2020.