| Word | Definitions | Synonyms |
|---|---|---|
| diopter | (noun) a unit of measurement of the refractive power of a lens which is equal to the reciprocal of the focal length measured in meters; used by oculists | Synonyms: dioptre |
| dioptre | (noun) a unit of measurement of the refractive power of a lens which is equal to the reciprocal of the focal length measured in meters; used by oculists | Synonyms: diopter |