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

To disappear gradually.

→ vanish.

Tending to → vanish gradually.

Verbal adj. from → evanesce.

A wave whose → amplitude → decreases → exponentially with distance from the → interface at which it is formed. Evanescent waves are formed when → sinusoidal waves are internally reflected off an interface at an angle greater than the → critical angle so that → total internal reflection occurs.

→ evanescent; → wave.

One of, usually three or four, diagonal supports that hold the → secondary mirror in a → reflecting telescope. Also called support vane.

M.E. spithre, O.E. M.E. spithra, akin to spinnan "to spin;" cf. M.L.G., M.Du., M.H.G., Ger. spinne, Du. spin "spider;" → vane.

Parré, → vane; târtan "spider," literally "weaver," composite word of with two cognate elements, the first one târ "thread, warp, string," related to tur "net, fishing net, snare," tâl "thread" (Borujerdi dialect), tân "thread, warp of a web," from the second element tan-, tanidan "to spin, twist, weave;" Mid.Pers. tanitan; Av. tan- to stretch, extend;" cf. Skt. tan- to stretch, extend;" tanoti "stretches," tántra- "warp; essence, main point;" Gk. teinein "to stretch, pull tight;" L. tendere "to stretch;" Lith. tiñklas "net, fishing net, snare," Latv. tikls "net;" PIE base *ten- "to stretch."

1) A blade attached radially to a central axis, as in a windmill, propeller, revolving fin, or the like. → spider vane.
2) → wind vane.
3) The flat part of a bird's → feather.

M.E., from O.E. fana "flag;" cognate with Ger. Fahne "flag," Gothic fana "piece of cloth."

Parré, from parr, → feather.

An object that is balanced on a rotating axis and indicates the direction of the wind. Also called a weather vane.

→ wind + vane "a blade, plate," O.E. fanafana "piece of cloth," O.H.G. fano, Ger. Fahne "flag, standard."

Bbâdnemâ "wind indicator," from bâd, → wind, + nemâ, from nemudan, → planetarium.