(?), n. [Gr. = dia` through + to see: cf. F. dioptase.] (Min.) A hydrous silicate of copper, occurring in emerald-green crystals.





(?), } n. [L. dioptra, fr. Gr. . See 2d Dioptric.] An optical instrument, invented by Hipparchus, for taking altitudes, leveling, etc.
[1913 Webster]


(?), n. [F. See 2d Dioptric.] (Optics) A unit employed by oculists in numbering glasses according to the metric system; a refractive power equal to that of a glass whose principal focal distance is one meter.
[1913 Webster]


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