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abbreviation, in writing, arbitrary shortening of a word, usually by cutting off letters from the end, as in U.S. and Gen. (General). Contraction serves the same purpose but is understood strictly to be the shortening of a word by cutting out letters in the middle, the omission sometimes being indicated by an apostrophe, as in the word don't. Most abbreviations are followed by a period. Usage, however, differs widely, and recently omission of periods has become common, as in NATO and UN. Acronyms are combinations of the first letters/syllables in a group of words to form a new grouping of letters that can be pronounced as a word. A period is never used when apostrophes appear. A list of abbreviations used in this encyclopedia may be found in the prefatory matter.
expansion, in physics, increase in volume resulting from an increase in temperature. Contraction is the reverse process. When heat is applied to a body, the rate of vibration and the distances between the molecules composing it are increased and, hence, the space occupied by the body, i.e., its volume, increases. This increase in volume is not constant for all substances for any given rise in temperature, but is a specific property of each kind of matter. For example, zinc and lead undergo greater expansion in a one-degree rise in temperature than do silver or brass. Since solids have a definite shape, each linear dimension of the solid increases by a proportional amount for a given temperature increase. The amount that a unit length along any direction of a substance increases for a temperature increase of one degree is called the coefficient of linear expansion of the substance. Most liquids also expand when heated. However, since liquids do not have a definite shape, it is the expansion of their volume as a whole that is relevant rather than the increase in a linear dimension. The amount of expansion that a unit volume (e.g., a cubic centimeter or a cubic foot) of any substance undergoes per one-degree rise in temperature is called its volume coefficient or coefficient of cubical expansion and is listed as a property of that substance. The coefficient of linear expansion can be calculated by dividing the coefficient of cubical expansion of the substance by three. When the amount of expansion of a given length of a substance has been determined experimentally, the linear coefficient is calculated by dividing the total amount of expansion by the product of the original number of length units and the number of degrees of rise in temperature. Gases also exhibit thermal expansion. The coefficient of expansion is about the same for all the common gases at ordinary temperatures; it is 1-273 of the volume at 0℃ per degree rise in temperature. The Kelvin, or absolute, scale is based upon this behavior (see Kelvin temperature scale). Charles's law concerning the expansion of gases states that the volume of a gas is directly proportional to its absolute temperature (see gas laws). Liquids differ from each other as do solids in their expansion coefficients. Water, unlike most substances, contracts rather than expands as its temperature is increased from 0℃ to 4℃; above 4℃ it exhibits normal behavior, expanding as the temperature increases.
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A microfilm defect in the form of a compressed image that occurs when the film speed is reduced as the document passes through a rotary microfilmer.
A function f from a metric space to itself for which there is a constant K that is less than 1 such that, for any two elements in the space, a and b, the distance between f (a) and f (b) is less than K times the distance between a and b.
The action or process of becoming smaller or pressed together, as a gas on cooling.
Shortening of the fibers of muscle tissue.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
Of concrete, the sum of volume changes occurring as the result of all processes affecting the bulk volume of a mass of concrete.
McGraw-Hill Dictionary of Architecture and Construction. Copyright © 2003 by McGraw-Hill Companies, Inc.
1. Physiol any normal shortening or tensing of an organ or part, esp of a muscle, e.g. during childbirth
2. Pathol any abnormal tightening or shrinking of an organ or part
Collins Discovery Encyclopedia, 1st edition © HarperCollins Publishers 2005
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