MCGRAW-Hill
`ICTIONARY Of
`CIENTlflC AND
`ECHNICAI
`ERMS
`Fifth Edition
`
`Sybil P. Parker
`Editor in Chief
`
`

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`On the cover: Photomicrograph of crystals of vitamin B1•
`(DennIs Kunkel, University of Hawaii )
`
`Included in this Dictionary are definitions which have been published previously in the following works: p, B.
`Jordain, Condensed Computer Encyclopedia. Copyright © 1969 by McGraw,Hill. Inc. All rights reserved. J.
`Markus. Electronics and Nucleonics Dictionary. 4th ed .• Copyright © 1960, 1966, 1978 by McGraw-Hili, Inc.
`All rights reserved. 1. Quick. Artists' and Illustrators' Encyclopedia, Copyright © 1969 by McGraw-Hili, Inc. All
`rights reserved. Blakiston' s Gould Medical Dictionary, 3d ed., Copyright © 1956, 1972 by McGraw-Hili, Inc. All
`rights reserved. T. Baumeister and L. S. Marks. eds., Standard Handbook for Mechanical Engineers, 7th ed.,
`Copyright © 1958, 1967 by McGraw-Hili, Inc. All rights reserved.
`
`In addition, material has been drawn from the following references: R. E. Huschke, Glossary of Meteorology,
`American Meteorological Society, 1959; U.S. Air Force Glossary of Standardized Terms, AF Manual II-I, vol.
`I, 1972; Communications-Electronics Terminology. AF Manual II~ I, vol. 3, 1970; W. H. Allen, ed .. Dictionary
`of Technical Terms for Aerospace Use, 1st ed., National Aeronautics and Space Administration. 1965; J. M,
`Gilliland. Solar-Terrestrial Physics: A Glossary of Terms and Abbreviations, Royal Aircraft Establishment Tech­
`nical Report 67158, 1967; Glossary ofAir Traffic Control Terms. Federal Aviation Agency; A Glossary of Range
`Terminology. White Sands Missile Range, New Mexico. National Bureau of Standards, AD 467-424; A DOD
`Glossary of Mapping. Charting and Geodetic Terms, 1st ed., Department of Defense, 1967; P. W. Thrush, compo
`and ed., A Dictionary of Mining, Mineral. and Related Terms. Bureau of Mines, 1968; Nuclear Terms: A Glossary,
`2d ed., Atomic Energy Commission; F. Casey, ed., Compilation of Terms in Information Sciences Technology,
`Federal Council for Science and Technology, 1970; GlossaryofStinfo Terminology, Office of Aerospace Research,
`U.S. Air Force, 1963; Naval Dictionary ofElectronic, Technical. and Imperative Terms, Bureau of Naval Person­
`nel, 1962; ADP Glossary, Department of the Navy, NAVSO P~3097.
`
`McGRAW-HILL DICTIONARY OF SCIENTIFIC AND TECHNICAL TERMS,
`Fifth Edition
`Copyright © 1994, 1989, 1984, 1978. 1976, 1974 by McGraw-Hili, Inc. All rights reserved. Printed in the United
`States of America, Except as pennilled under the United States Copyright Act of 1976. no part of this publication
`may be reproduced or distributed in any form or by any means, or stored in a database or retrieval system, without
`the prior written pennission of the publisher.
`
`234567890
`
`DOW/DOW
`
`9987654
`
`ISBN 0-07-042333-4
`
`Library of Congress Cataloging-in-Publication Data
`
`McGraw-Hili dictionary of scientific and technicaltenns I
`Sybil P. Parker. editor in chief..-5th ed.
`p.
`cm.
`
`ISBN 0-07-042333-4
`
`I. Science-Dictionaries. 2. Technology-Dictionaries.
`I. Parker, Sybil P.
`
`Q123.M34 1993
`
`503-dc20
`
`93-34772
`
`CIP
`
`,'
`
`INTERNATIONAL EDITION
`
`Copyright © 1994. Exclusive rights by McGraw-Hili, Inc. for manufacture and export. This book cannot be re­
`exported from the country to which it is consigned by McGraw-Hill. The International Edition is not available in
`North America,
`
`When ordering this title, use ISBN 0-07-113584~7.
`
`

`
`o
`
`section line
`
`security kernel
`
`securitJ
`
`[CIV ENG] A line representing the boundary of a
`section line
`section of land.
`[GRAPHICS] One of a series of parallel lines
`indicating a cut surface in a mechanical or architectural drawing.
`{ 'sek'sh<ln ,lIn I
`.
`section modulus
`[MECH} The ratio of the moment of inertia
`of the cross section of a beam undergoing flexure to the greatest
`distance ofan element of the beam from the neutral axis. {'sek'
`sh<ln 'miij';}'I<ls I
`sector
`[COMPUT scI] 1. A portion of a track on a magnetic
`disk or a band on a magnetic drum. 2. A unit of data stored in
`such a portion.
`[CIY ENG] A clearly defined area or airspace
`designated for a particular purpose.
`[ELECTROMAG] Coverage
`of a radar as measured in azimuth.
`[MATH] A portion of a
`circle bounded by two radii and an arc joining their end points.
`[METEOROL] Something resembling the sector of a circle, as a
`warm sector between the warm and cold fronts of a cyclone.
`{ 'sek·t<lr I
`sectoral harmonic [MATH] A spherical harmonic which is 0
`on a set of equally spaced meridians of a sphere with center at
`the origin of spherical coordinates, dividing the sphere into
`sectors. {:sek·t<l~1 har'miin'ik I
`sectoral hom
`[ELECTROMAG] Horn with two opposite sides
`parallel and the two remaining sides which diverge. {'sek·t<l·
`f<ll 'hOrn I
`sector boundary [ASTROPHYS] The rapid transition from one
`polarity to another in the interplanetary magnetic field. {'sek'
`t<lr ,bailll'dre )
`sector disk
`[PHYS] A device used to reduce the intensity of
`a beam of light or other electromagnetic radiation by an accu­
`rately known amount; in its simplest form, it consists of a cir­
`cular, opaque disk with one or more sectors cut out of it, rapidly
`rotating in the path of the beam. {'sek,t<lr ,disk }
`sector display
`[ELECTR] A display in which only a sector of
`the total service area of a radar system is shown; usually the
`sector is selectable. {'sek·t<lrdi,spla)
`sectored light [NAv] A light having sectors ofdifferent colors
`orof the same color in specific sectors separated by dark sectors.
`{ 'sek,t:lrd 'lIt I
`sector gate [CIV ENG] A horizontal gate with a pie-slice cross
`section used to regulate the level of water at the crest of a dam:
`it is raised and lowered by a rack and pinion mechanism. {'sek'
`t:lr ,gat}
`[DES ENG] 1. A toothed device resembling a
`sector gear
`portion of a gear wheel containing the center bearing and a part
`of the rim with its teeth. 2. A gear having such a device as its
`chief essential feature.
`[MECH ENG] A gear system employing
`such a gear as a principal part. {'sek·t:lr ,gir }
`sectorgram See pie chart. {'sek·t<lr,gram}
`sector interleave
`[COMPUT SCI] A sequence indicating the
`order in which sectors are arranged on a hard disk, generally so
`as to minimize access times. Also known as sector map.
`[ 'sek·t:lr 'in·t:lr,lev }
`sector map See sector interleave. {'sek·t:lr ,map}
`sector mark
`[COMPUT SCI] A location on each sector of each
`track ofa disk pack or floppy disk that gives the sector's address,
`tells whether the sector is in use, and gives other control infor­
`mation.
`('sek·t<lr ,mark)
`sector of fire
`[ORD] An area which is required to be covered
`by fire by an individual, a weapon, or a unit. {'sek·t:lr:lv 'fir J
`sector scan
`[ELECTR] A radar scan through a limited angle,
`as distinguished from complete rotation. {'sek·t:lr ,skan }
`sectorsearch [NAv] A flight or sailing plan of three legs, the
`turning points being at equal distances along radial lines from a
`fixed or moving point. {'sek·t:lr ,s:lrch }
`sector structure
`[ASTROPHYS] The polarity pattern of the
`interplanetary magnetic field observed during a solar rotation.
`{ 'sek·t:lr ,str~k'ch:lr )
`sector wind
`[METEOROL] The average observed or computed
`wind (direction and speed) at flight level for a given sector of
`an air route; sectors for over-ocean flights usually consist of 10·
`of longitude. {'sek·t~r ,wind}
`secular
`[ENG] Of or pertaining to a long indefinite period of
`time. {'sek'y:l'l~r}
`[ASTRON] An apparent gradual accel­
`secular acceleration
`eration of the moon's motion in its orbit, as measured relative
`to mean solar time. {'sek'y:l'lar ak,sel':l'rli'sh:ln )
`secular determinant
`[MATH] For a square matrix A, the de­
`terminant of the matrix whose off-diagonal components are
`equal to those of A, and whose diagonal components are equal
`
`to the difference between those of A and a parameter A; it is
`equal to the characteristic polynomial in A of the linear trans­
`formation represented by A. {'sek'Y:l'):lr di'br-m~n':lnt }
`secular equilibrium
`[NUCLEO] Radioactive equilibrium in
`which the parent has such a small decay constant that there has
`been no appreciable change in the quantity of parent present by
`the time the decay products have reached radioactive equilib­
`rium. {'sek-Y:l·I:lr ,e'kw:l'lib-re':lm }
`secular parallax
`[ASTRON] An apparent angular displace­
`ment of a star, resulting from the sun's motion. {'sek'Y:l'I:lr
`'par-:l,laks }
`[ASTROPHYS] Changes in the orbit of
`secular perturbations
`a planet, or of a satellite, that operates in extremely long cycles.
`{ 'sek'Y:l'!<lr ,p:lN:lr'ba'sh;::,llZ }
`secular trend
`[STAT] A concept in time series analysis that
`refers to a movement or trend in a series over very long periods
`of time. Also known as long-time trend. {'sek·Y:l·I:lr 'trend}
`secular variable
`[ASTRON] A star whose brightness appears
`to have slowly lessened or increased over a time period of
`centuries. {'sek'Y:l'I:lr 'ver'e':l'b:ll J
`secular variation
`[ASTRON] A perturbation of the moon's
`motion caused by variations in the effect of the sun's gravita­
`tional attraction on the earth and moon as their relative distances
`from the sun vary during the synodic month.
`[GEOPHYS] The
`changes, measured in hundreds of years, in the magnetic field
`of the earth. Also known as geomagnetic secular variation.
`{ 'sek'Y:l'I:lr ,ver-e'a'sh<ln }
`secund
`[BOT] Having lateral members arranged on one side
`only. {'se,k:lnd I
`secundine dike
`[GEOL] A dike which has been intruded into
`hot country rock. {'sek':ln,dIn 'dIk }
`secure
`[ORD] To gain possession of a position or terrain
`feature, with or without force, and to make such disposition as
`will prevent, as far as possible, its destruction or loss by enemy
`action. {si'kyur }
`[COMMUN] The transmis­
`secure visual communications
`sion of an encrypted digital signal consisting of animated visual
`and audio information: the distance may vary from a few hun­
`dred feet to thousands of miles. {si'kyilr 'vizh'<l'w<ll k<l,myu'
`M'ka'sh:lnz J
`[COMMUN] Voice message that is scrambled or
`secure voice
`coded. therefore not transmitted in the clear. {si'kyiu" 'vois I
`[PHARM] C 13HI5N02 A crystalline compound
`securlnine
`that forms yellow crystals from a methanol solution and melts
`at 142-143"C; used to make the nitrate compound for cardiac
`insufficiency. {si'kYUr-<l,nen}
`securlte explosive [MATER] A type of plastic explosive with
`a balanced oxygen content; it is built up on a nonexplosive,
`hydrophilic gel and contains oxygen-emitting salts, solid high
`explosive, and water. {si'kyilr,It ik,splO'siv J
`security
`[COMPUT SCI] The existence and enforcement of
`techniques which restrict access to data, and the conditions un­
`der which data may be obtained.
`[ELEe] The ability of an
`electric power system to suitably respond to disturbances arising
`within that system, including both local and widespread distur­
`bances and the loss of major generation and transmission facil­
`ities.
`[ORD] 1. Measures taken by a command to protect itself
`from espionage, observation. sabotage, annoyance. or surprise.
`2. A condition which results from the establishment and main­
`tenance of protective measures which ensure a state of inviola­
`bility from hostile acts or influences. 3. Protection of supplies
`or supply establishments against enemy attack, fire, theft, and
`sabotage. {si'kyur- :ld'e }
`security classification
`[ORD] A category Of grade assigned
`to defense information or materiel to indicate the degree of
`danger to national security that would result from its unauthor·
`ized disclosure and the standard of protection required to guard
`[si 'kyilr-:ld'e ,klas':l'f~'kli'
`against unauthorized disclosure.
`sh;::,n I
`[ORD] A clearance given to a person to
`security clearance
`pennit access to classified material, equipment. or information
`up to and including a given classification, provided the person
`can establish a need-Io-know. {si'kyur-:ld'e ,klir-:lns I
`security control officer
`In the United States, an offi·
`[ORD]
`cer, warrant officer, or responsible civilian official appointed in
`each command or agency to exercise staff supervision over the
`safeguarding of defense information. {si'kyUr-~d'e k~n'trOl
`,Of':l's;::,r)
`security kernel
`
`[COMPUT SCI] A portion of an operating sys­
`
`tern into wb
`trated' fom:
`arate from I
`security rC\
`communicl
`bases and,
`location. OJ
`eral locatio
`warningtlu
`ilJ ,sis·t~m
`SED See sk
`sedation
`
`I
`sedative
`
`on the cent
`
`Sedentaria
`annelids it
`less romp!
`tures, or d
`posterior a
`sedentary
`which it w
`sediflucti~
`of materia
`mary stag{
`sediment
`fragmente,
`from weal
`dropped b
`any other
`surface SI.!
`material tl
`the liquid
`sediment!
`that are la
`of sedime
`ical sortin
`fragments
`mixed tog
`stone coni
`sedimenb
`tril 'sI'k~1
`sediment
`ration (b;
`mass into
`resorted ~
`areas. {
`sediment
`material t
`rock in til
`filling of,
`sediment!
`sediment!
`sediment
`fromanol
`paleontol>
`sediment
`sh:ln J
`sediment
`mentaryr
`as by inti
`sidence d
`in'sar-sh.
`sediment
`zh:ln)
`sediment
`mentary
`highpw
`bedding
`very irrei
`sedimen'
`potential
`tion. {
`sedimen
`sificatiOi
`raphy.
`sedimen
`tion, ern
`rocks.