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American Heritage Dictionary - Cite This Source - Share This

ze·nith       (zē'nĭth)  Pronunciation Key  n.   The point on the celestial sphere that is directly above the observer. The upper region of the sky. The highest point above the observer's horizon attained by a celestial body. The point of culmination; the peak: the zenith of her career. See Synonyms at summit. [Middle English senith, from Old French cenith, from Medieval Latin, from Arabic samt (ar-ra's), path (over the head), from Latin sēmita, path; see mei-1 in Indo-European roots.]

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zenith 

WordNet - Cite This Source - Share This

zenith

noun

the point above the observer that is directly opposite the nadir on the imaginary sphere against which celestial bodies appear to be projected [ant: nadir]

The American Heritage Science Dictionary - Cite This Source - Share This

zenith       (zē'nĭth)  Pronunciation Key  The point on the celestial sphere that is directly above the observer (90 degrees above the celestial horizon). Compare nadir.

Webster's Revised Unabridged Dictionary - Cite This Source - Share This

Zenith

Az"i*muth\, n. [OE. azimut, F. azimut, fr. Ar. as-sum?t, pl. of as-samt a way, or perh., a point of the horizon and a circle extending to it from the zenith, as being the Arabic article: cf. It. azzimutto, Pg. azimuth, and Ar. samt-al-r[=a]'s the vertex of the heaven. Cf. Zenith.] (Astron. & Geodesy) (a) The quadrant of an azimuth circle. (b) An arc of the horizon intercepted between the meridian of the place and a vertical circle passing through the center of any object; as, the azimuth of a star; the azimuth or bearing of a line surveying.

Note: In trigonometrical surveying, it is customary to reckon the azimuth of a line from the south point of the horizon around by the west from 0[deg] to 360[deg].

Azimuth circle, or Vertical circle, one of the great circles of the sphere intersecting each other in the zenith and nadir, and cutting the horizon at right angles. --Hutton.

Azimuth compass, a compass resembling the mariner's compass, but having the card divided into degrees instead of rhumbs, and having vertical sights; used for taking the magnetic azimuth of a heavenly body, in order to find, by comparison with the true azimuth, the variation of the needle.

Azimuth dial, a dial whose stile or gnomon is at right angles to the plane of the horizon. --Hutton.

Magnetic azimuth, an arc of the horizon, intercepted between the vertical circle passing through any object and the magnetic meridian. This is found by observing the object with an azimuth compass.

On-line Medical Dictionary - Cite This Source - Share This

zenith

zenith: in CancerWEB's On-line Medical Dictionary