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1. One eighth of a circle.
a. A 45° arc.
b. The area enclosed by two radii at a 45° angle and the intersected arc.
3. An instrument based on the principle of the sextant but employing only a 45° angle, used as an aid in navigation.
4. Astronomy The position of a celestial body when it is separated from another by a 45° angle.
5. One of eight parts into which three-dimensional space is divided by three usually perpendicular coordinate planes.

[Latin octāns, octant-, from octō, eight; see oktō(u) in Indo-European roots.]

oc·tan′tal (ŏk-tăn′təl) adj.
American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.


1. (Mathematics) maths
a. any of the eight parts into which the three planes containing the Cartesian coordinate axes divide space
b. an eighth part of a circle
2. (Astronomy) astronomy the position of a celestial body when it is at an angular distance of 45° from another body
3. (Navigation) an instrument used for measuring angles, similar to a sextant but having a graduated arc of 45°
[C17: from Latin octans half quadrant, from octo eight]
Collins English Dictionary – Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014


(ˈɒk tənt)

1. the eighth part of a circle.
2. any of the eight parts into which three mutually perpendicular planes divide space.
3. an instrument having an arc of 24°, used by navigators for measuring angles up to 90°.
4. the position of one heavenly body when 45° distant from another.
[1680–90; < Latin octant-, s. of octāns=oct(ō) eight + -āns, as in quadrāns quadrant]
oc•tan′tal (-ˈtæn tl) adj.
Random House Kernerman Webster's College Dictionary, © 2010 K Dictionaries Ltd. Copyright 2005, 1997, 1991 by Random House, Inc. All rights reserved.
ThesaurusAntonymsRelated WordsSynonymsLegend:
Noun1.octant - a measuring instrument for measuring angles to a celestial bodyoctant - a measuring instrument for measuring angles to a celestial body; similar to a sextant but with 45 degree calibration
limb - the graduated arc that is attached to an instrument for measuring angles; "the limb of the sextant"
measuring device, measuring instrument, measuring system - instrument that shows the extent or amount or quantity or degree of something
Based on WordNet 3.0, Farlex clipart collection. © 2003-2012 Princeton University, Farlex Inc.
References in classic literature ?
It was in its octant, and showed a crescent finely traced on the dark background of the sky.
Pass one and two used an octant search, to effectively deal with the declustered data and restricted the selection of samples to a maximum of 12 samples per drill hole.
Houlihan Lokey, Credit Suisse Securities (USA) LLC, Octant Partners and Milbank, Tweed, Hadley & McCloy LLP advised Mill Rock on the transaction.
Houlihan Lokey, Credit Suisse Securities LLC, Octant Partners and Milbank, Tweed, Hadley and McCloy LLP advised Mill Rock on the transaction.
Also named as a respondent is Octant Builders president Rowena Manzano.
Roland Cortez, NCMH medical chief II, filed a complaint at the Office of the Ombudsman on Monday (July 15) against NCMH chief administrative officer Clarita Avila citing findings made by the National Bureau of Investigation (NBi) on irregularities in the award of the project to extend NCMH's Pavilion 6 to Octant Builders.
2a); however, in problems with three objectives, [conjunction] is considered as the first octant of the unit sphere (see Figure.
That there is a definite portion of low pressure within which conditions for the development of tornadoes are most favorable; and this has been called the "dangerous octant "
Miss Whyte said the case came to light as allegations built over time, resulting in Operation Octant, after the number of complainants continued to grow from 2014 onwards.
The scatterplots of the velocity perturbation components in three mutually perpendicular planes indicate that the rocket body exploded in the 'Octant model' of exploding tanks.
The principle of competitive exclusion was reexamined by Koch [1] in 1974 who found via numerical simulation that the coexistence of two predators competing exploitatively for a single prey species in a constant and uniform environment was in fact possible when the predator functional response to the prey density was assumed according to nonlinear function, and such coexistence occurred along what appeared to be a periodic orbit in the positive octant of [R.sup.3] rather than an equilibrium.
Notice that the experiments cannot discover the correct octant of [[theta].sub.23] at 3[sigma]; that is, they cannot tell if [[theta].sub.23] > [pi]/4 (High Octant) or [[theta].sub.23] < [pi]/4 (Lower Octant) unless they are supplemented by an external prior.