▪ I. sector, n.
(ˈsɛktə(r))
[a. late L. sector (Boethius), a special use of L. sector (agent-n. f. secāre to cut), to translate Gr. τοµεύς, lit. ‘cutter’, but used by Archimedes and later geometers in the senses 1 a and 1 b. Cf. F. secteur, Sp. sector, It. settore.]
I. 1. Geom. a. A plane figure contained by two radii and the arc of a circle, ellipse, or other central curve intercepted by them.
| 1570 Billingsley Euclid iii. Def. ix. 83 A Sector of a circle. 1660 Barrow Euclid iii. Def. ix, A sector of a circle is when an angle is set at the center of that circle. 1834 Nat. Philos. III. Hist. Astron. xvi. 85/1 (U.K.S.) The sector described by its radius vector in a given time round the earth is not changed. 1880 Williamson in Encycl. Brit. XIII. 50/2 The area of the elliptic sector APCP. |
b. sector of a sphere: a solid generated by the revolution of a plane sector about one of its radii.
| 1656 tr. Hobbes' Elem. Philos. (1839) 371 The centre of equiponderation of the sector of a sphere. 1706 Phillips (ed. Kersey), Sector of a Sphere, is a Conical Solid, whose Vertex or Top ends in the Center of the Sphere, and its Base, or Bottom, is a Segment of the same Sphere. 1840 Lardner Geom. 217 The sector of a sphere consists of a cone and a spherical segment. |
2. A body or figure having the shape of a sector; hence, a division or part, a unit.
a. gen. Any piece of mechanism so shaped.
| 1715 Desaguliers Fires Impr. 122 At the under side of this Trap-Door, on each side have a small portion of a Circle, or a Sector, whose Center is at that part of the Trap-Door where the Hinge is. 1824 R. Stuart Hist. Steam Engine 145 The double impulse was communicated to the working-beam by the intervention of a sector placed on the end of the pump-rod, working into a sector placed on the end of the working-beam. 1904 Brit. & Col. Printer 10 Mar. 14/2 A toothed sector having a pin and slot connection with it gives the required shift to the slide. |
b. Optics. A division of a disc of paper or other material used in certain demonstrations.
| 1831 Brewster Optics vii. 70 The same result will be obtained, if we take a circle of paper and divide it into sectors of the same size as the coloured spaces. 1865 Tyndall Fragm. Sci. (1876) 311 A disk with differently-coloured sectors is caused to rotate rapidly. |
c. Astr. (See
quot. 1863.)
| 1840 Dick Sider. Heavens 447 It appears..that one of these luminous fans or sectors was observed by Sir J. Herschel. 1863 Hind Introd. Astron. (ed. 3) 205 Sector, Luminous, in the head of a comet, is an emanation from the nucleus brighter than the rest of the coma in the form of a fan or sector. |
d. Electr. A small piece of ebonite forming part of a Bertsch machine.
| 1894 S. R. Bottone Electr. Instr. Making 40 This little piece of ebonite (technically known as the ‘sector’) and its stand must be attached to the base board... Opposite this sector, but on the other side of the glass plate, is a ‘comb’. |
e. Path. A portion of the field of vision cut off in certain diseases of the optic nerve.
| 1899 Allbutt's Syst. Med. VI. 842 There was enormous swelling of the left optic nerve, coupled with loss of a large sector of the temporal portion of the field [of vision]. |
f. Ent. (See
quot. 1861.)
| 1861 H. Hagen Synopsis Neuroptera N. Amer. 343 Sectors, longitudinal nerves which strike the principal nerves at an angle, and usually reach the apex or hind margin of the wing. |
g. (
a)
Mil. A part or section of a front, corresponding generally to a sector of a circle the centre of which is a headquarters.
| 1916 ‘Boyd Cable’ Action Front 237 The Colonel was..vainly trying to recall any sap-head within his sector of line. 1917 W. J. Locke Red Planet xiv. 161 Somewhere in this region—or sector, as we call it nowadays—there was a certain bit of ground that had been taken and retaken over and over again. 1930 S. Sassoon Mem. Infantry Officer iv. 61 Rose Trench..and Willow Avenue, were among the first objectives in our sector [of the Somme attack]. |
(
b) A part or branch of an economy, or of a particular industry or activity. Freq. in phrases
private sector (see
private a. 7 j),
public sector (see
public a. 2 j).
| 1937 A. Huxley Ends & Means xii. 196 The accomplished intellectual understands the relations subsisting between many sectors of apprehended reality. 1950 Hansard Commons 7 Mar. 183 Every Member of this House..could point to examples of gross feather bedding both in Government Service, in the socialised sector of the economy and in private industry. 1959 Listener 5 Nov. 767/2 Problems of a comparable nature in other sectors of industry. 1964 Ann. Reg. 1963 195 The Government's failure to carry out its declared aims—land reform..and planned development in all sectors of the economy—was to some extent caused by the President's readiness to yield too easily to pressure. 1980 Sci. Amer. Sept. 134/1 This development is the outcome of an explicit long-term policy to establish an adequate indigenous capacity in all the basic sectors, particularly metals and machinery, heavy chemicals. |
(
c)
gen. One of the regions or districts into which a geographical area has been divided.
| 1943 H. A. Wallace Century of Common Man (1944) 82 The ignorance that clouds many communities in many sectors of our own nation. 1958 Listener 9 Oct. 547/1 It has recently become fashionable to divide the Middle East into two major entities: the Arab sector and the non-Arab sector. 1971 Daily Tel. 12 Apr. 2/1 Experts believe nearly half of the country's daily oil consumption will be produced from the British sector of the sea by 1976. |
h. Computers. A subdivision of a track on a magnetic drum or disc, or the block of data stored on it.
| 1958 Computer Jrnl. I. 128/1 Information is stored on ‘sectors’, each capable of containing 32 numbers... There are 1,024 such sectors, two to each track on a drum. 1962 Gloss. Terms Automatic Data Processing (B.S.I.) 68 Sector, a specified part of a track or band on a magnetic disc or drum store: hence, in programming, a deprecated alternative name for a block applied to the group of words stored on a sector. 1976 G. Wiederhold Database Design ii. 40 If tracks cannot be divided by hardware into sectors, system software may divide a track into smaller units. |
i. Gram. The position in a sentence normally occupied by any one of the basic units of which the sentence is composed.
Cf. sector analysis, sense 3 below.
| [1955 E. H. Jorden Syntax Colloq. Jap. v. 13 Evidence furnished by focus-classes indicates that minor sector boundaries should be observed even here—that the IC division should occur between the gerund of the copula and the following verb, where the sector boundary occurs.] 1966 R. L. Allen Verb Syst. Present-Day Amer. Eng. iii. 88 An examination of a large number of sequences suggests that in most non-literary sentences there is a kind of ‘spectrum’ of basic positions, which may be called ‘sectors’. 1968 R. Crymes Some Syst. Substitution Correlations in Mod. Amer. Eng. ii. 36 The major positions in the major English sentence, which is a sentence having time orientation [,]..exist in fixed sequence, and they are called sectors. 1974 Chisholm & Milic Eng. Lang. vii. lii. 424 According to the grammatical description called Sector Analysis, the English sentence consists of ten sectors. |
3. attrib. and
Comb., as
sector-like,
sector-shaped adjs.;
sector analysis Gram., the analysis of sentences in terms of the positions occupied by the basic units of which they are composed (
cf. sense 2 i above);
sector machine (see
quot. 1888);
sector-piece, a sector-shaped portion of any object;
sector scanning, scanning with radar, sonar, or the like in which the detector rotates to and fro through a fixed angle; so
sector scan n. (
freq. attrib., with hyphen).
| 1966 R. L. Allen Verb Syst. Present-Day Amer. Eng. iii. 88 The order..of the occupied sectors remains constant... Many of the details of this ‘*sector’ analysis lie beyond the scope of the present study. 1971 D. T. Bình Tagmemic Comparison of Structure of Eng. & Vietnamese Sentences iii. 66 Sector analysis..primarily emphasizes the positions of units on the sentence, trunk, and predicate..levels. 1977 Amer. Speech 1975 L. 127 Only the concluding chapters give any attention to the problems of composition, and much of this is a discussion of sector analysis. |
| 1899 Allbutt's Syst. Med. VII. 318 Occasionally, instead of complete blindness of one-half of the visual field, *sector, or quadrant-like defects are found in the upper or lower half. |
| 1888 Jacobi Printers' Voc., *Sector machine, a cylindrical printing machine. |
| 1715 Desaguliers Fires Impr. 122 Fix a couple of Springs under the Frame, each of which must bear against the Limbs of the *Sector-Pieces. 1902 Orde-Browne Armour in Encycl. Brit. XXV. 670/2 Before adoption a sector piece was subjected to three blows from projectiles fired from an Elswick 100-ton breech-loading gun. |
| 1946 Radar: Summary Rep. & Harp Project (U.S. Nat. Defense Res. Comm.) 143/2 *Sector scan, motion of the scanner reflector back and forth through a limited angle, instead of through 360°. 1969 R. P. Selby in C. J. Richards Mech. Engin. in Radar & Communications ix. 387 Radar installations used for air-traffic control are sometimes required to operate on demand in sector-scan mode, the area of scan usually not exceeding 20° and the rate of scan approximately 20 scans per minute. 1978 Nature 9 Nov. 174/1 A simple sector scan mode is used, at a frequency of 1 Hz, with the target coupled acoustically to the transducer with water. |
| 1946 Princ. & Applic. of Underwater Sound (U.S. Nat. Defense Res. Comm.) (1968) xi. 213/1 A plan position indicator is..required for *sector scanning, the CRO spot..tracing a synchronous map of the motion of the active region. 1969 R. P. Selby in C. J. Richards Mech. Engin. in Radar & Communications ix. 386 It is sometimes required to move an antenna system about a vertical axis in an oscillatory mode (sector-scanning), thereby turning the antenna through a limited arc in either direction. 1974 Y. Kikuchi in G. W. Stroke et al. Ultrasonic Imaging & Holography 267 Asberg has been proposing a high speed sector scanning of a focusing mirror system receiver for obtaining an ultrasonic cinematogram of the living heart. 1977 Navy News July 18/2 Because the number of wrecks on our continental shelf is so high..modern equipment such as Hydrosearch—the British sector-scanning surveying sonar—is particularly needed. |
| 1902 Orde-Browne Armour in Encycl. Brit. XXV. 670/2 The joints shown in this figure indicate that the turret roof is built up of fifteen *sector-shaped pieces. |
II. 4. A mathematical instrument, invented by Thomas Hood (see
quot. 1598) and improved by Edmund Gunter, used for the mechanical solution of various problems.
In its present form it consists of two flat rules stiffly hinged together, inscribed with various kinds of scales. In Hood's form, a graduated arc was an essential part of the instrument, and from some of the inventor's remarks it would appear that the name was given with reference to the form of the apparatus (see sense 1), not, as might be supposed, to its function in performing proportional division of lines.
| 1598 Hood Making & Use of Sector 1 A Sector is a mathematicall instrument consisting of 2. feete, one moueable, an other fixed, making an angle, and of a circumferentall Limbe. 1624 Gunter (title), The Description and use of the Sector, the Crosse-staffe, and other Instruments. 1673 E. Browne Trav. Germ., etc. (1677) 18 By applying an Instrument joynted like a Carpenters Rule, or a Sector, the Skin is held fast. 1766 Complete Farmer s.v. Surveying 7 G 1/1 If a little error be committed in making up the sector, the most of it goes off again in the substraction of the triangle. 1803 Phil. Trans. XCIII. 387 In the sector I am going to describe, Mr. Ramsden has obviated the inconveniences attendant on the use of former sectors. 1884 F. J. Britten Watch & Clockm. 233 The sector is really a proportional measuring gauge, suited for nearly all requirements of the watch and clock maker. |
| attrib. 1664 Wakely Mariners-Compass rectified (1694) 273 All Sector-Lines or Scales, meet at the center of the Head (where the Joint is) at the left-hand, and from thence are figured towards the right, each being twice repeated; that is, one on each Leg or Side of the Sector answering one another. Ibid. 274 The Use of the Sector-Lines for Projection. |
5. An astronomical instrument consisting of a telescope turning about the centre of a graduated arc. See dip-
sector, zenith-
sector.
| 1711 Hearne Collect. (O.H.S.) III. 129 By my Sector it is but 141. 1755 Gentl. Mag. XXV. 511 A sector of six feet radius, whose divided arc was somewhat more than 51 degrees. 1843 Penny Cycl.. XXVII. 765/2 Bradley's sector as originally made was not reversible, and therefore only fit for measuring differences or variations. 1877 Chambers Astron. 920 Astronomical Sector, an instrument for finding the distance between two objects whose distance is too great to be measured by means of a micrometer in a fixed telescope. |
Senses 2 h and i in
Dict. become 2 i and j. Add:
[I.] [2.] h. Aeronaut. A route or journey flown non-stop by a commercial airline, often as part of a longer flight schedule.
| 1950 Stroud & Mearles in James & Stroud World's Airways ii. 56/1 It was for the operation of the Singapore–Brisbane sector that the D.H.86 was designed. 1961 Observer 12 Feb. 1/5 The pilots claim that the four ‘sectors’ a day allotted to Comet pilots under the summer schedules are ‘too much’. A ‘sector’ is the journey between a take-off and a landing. 1976 Aviation Week 16 Feb. 22/3 For Europe in 1990, the predicted total of 435 billion seat miles offered is expected to be broken down to 250 billion seat miles for long-range routes and 185 billion seat miles on short/medium-range sectors. 1986 Aircraft Illustr. July 374/2 The series 3A-RA and 3B-RA had a range..of 1,770 statute miles, permitting..an unrefuelled sector from London to Istanbul. |
▪ II. sector, v. (
ˈsɛktə(r))
[f. sector n.] trans. To divide into sectors; to provide with sectors.
| 1884 F. J. Britten Watch & Clockm. 292 Circularly rounded pinions may be used as drivers if they are sectored large. 1902 W. D. Jones in Times 1 Dec. 15/2 It would appear that..the Belle Isle light..is not correctly sectored. |
▪ III. sector variant of
secutor Obs., executor.