An Etymological Dictionary of Astronomy and Astrophysics
English-French-Persian

Left to one's choice; not required or mandatory (Dictionary.com).

→ option; → -al.

Any of various instruments for measuring refractive errors of the eye.

From opto- "vision; eye; optis," combining form from Gk. optos "seen, visible," from opsesthai "be going to see," related to ops "eye;" → -meter.

Did, → vision; -sanj, → -meter.

The branch of optics concerned with the wave properties of light, → diffraction, → polarization, and other phenomena for which the ray approximation of → geometric optics is not valid. Also called → wave optics.

→ physical; → optics.

In general, pertaining to or affording an overall view.

M.L. synopticus, from Gk. synoptikos, from synop-, → synopsis, + -tikos.

1) Sun: A map that displays positions of certain events (e.g., → sunspots, → faculae, → filaments, etc.) observed during one solar rotation.
2) Meteorology: The use of data obtained simultaneously over a wide area for the purpose of presenting a comprehensive and nearly instantaneous picture of the state of the atmosphere.

→ synoptic; → map.

The branch of optics that analyzes the electromagnetic radiation in terms of its wave characteristics. Also called → physical optics.

→ wave; → optics.