# coefficient

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coefficient
1. The expression of the amount or degree of any quality possessed by a substance, or of the degree of physical or chemical change normally occurring in that substance under stated conditions. 2. The ratio or factor that relates a quantity observed under one set of conditions to that observed under standard conditions, usually when all variables are either 1 or a simple power of 10. [L. co- + efficio (exfacio), to accomplish]
- absorption c. 1. the milliliters of a gas at standard temperature and pressure that will saturate 100 mL of liquid; 2. the amount of light absorbed in passing through 1 cm of a 1 molar solution of a given substance, expressed as a constant in Beer-Lambert law; Cf.:specific absorption c.. 3. a measure of the rate of decrease of intensity of an x-ray beam in its passage through a substance, resulting from a combination of scattering and conversion to other forms of energy.
- activity c. (γ) activity (2).
- biological c. rarely used term denoting the energy expended by the body at rest.
- Bunsen solubility c. (α) the milliliters of gas STPD dissolved per milliliter of liquid and per atmosphere (760 mm Hg) partial pressure of the gas at any given temperature.
- c. of consanguinity SYN: c. of inbreeding.
- correlation c. a measure of association that indicates the degree to which two variables have a linear relationship; this c., represented by the letter r, can vary between +1 and −1; when r = +1, there is a perfect positive linear relationship in which one variable relates directly with the other; when r = −1, there is a perfect negative linear relationship between the variables.
- creatinine c. the number of milligrams of creatinine excreted daily per kilogram of body weight.
- diffusion c. the mass of material diffusing across a unit area in unit time under a concentration gradient of unity. SYN: diffusion constant.
- distribution c. the ratio of concentrations of a substance in two immiscible phases at equilibrium; the basis of many chromatographic separation procedures. SYN: partition c..
- economic c. in growth and cultivation of microorganisms, the ratio of the mass produced to the substrate consumed.
- extinction c. (ε) SYN: specific absorption c..
- extraction c. the percentage of a substance removed from the blood or plasma in a single passage through a tissue; e.g., the extraction c. for p-aminohippuric acid (PAH) in the kidney is the difference between arterial and renal venous plasma PAH concentrations, divided by the arterial plasma PAH concentration.
- filtration c. a measure of a membrane's permeability to water; specifically, the volume of fluid filtered in unit time through a unit area of membrane per unit pressure difference, taking into account both hydraulic and osmotic pressures.
- Hill c. the slope of the line in a Hill plot; a measure of the degree of cooperativity. SYN: Hill constant.
- hygienic laboratory c. SYN: Rideal-Walker c..
- c. of inbreeding the probability that the progeny of a consanguineous marriage will be homozygous for a specific autosomal allele derived from a common ancestor. SYN: c. of consanguinity.
- isotonic c. the amount of salts in the blood plasma, or the amount that should be added to distilled water in order to prepare an isotonic solution.
- c. of kinship the probability that two genes at the same locus, picked at random from each of two individuals, are identical by descent.
- lethal c. that concentration of disinfectant that kills bacteria at 20–25°C in the shortest period of time.
- linear absorption c. that fraction of ionizing radiation absorbed in a unit thickness of a substance or tissue. SEE ALSO: absorption c. (3). Cf.:attenuation.
- Long c. SYN: Long formula.
- molar absorption c. (ε) absorbance (of light) per unit path length (usually the centimeter) and per unit of concentration (moles per liter); a fundamental unit in spectrophotometry. SYN: absorbancy index (2), absorptivity (2), molar absorbancy index, molar absorptivity, molar extinction c..
- Ostwald solubility c. (Λ) the milliliters of gas dissolved per milliliter of liquid and per atmosphere (760 mm Hg) partial pressure of the gas at any given temperature. This differs from Bunsen solubility c. (α) in that the amount of dissolved gas is expressed in terms of its volume at the temperature of the experiment, instead of STPD. Thus, λ = α (1 + 0.00367t), where t = temperature in degrees Celsius.
- oxygen utilization c. the extraction c. for oxygen in any given tissue.
- partition c. SYN: distribution c..
- permeability c. a c. associated with simple diffusion through a membrane that is proportional to the partition c. and the diffusion c. and inversely proportional to membrane thickness.
- phenol c. SYN: Rideal-Walker c..
- Poiseuille viscosity c. an expression of the viscosity as determined by the capillary tube method; the c. η = (πPr4t8vl), where P is the pressure difference between the inlet and outlet of the tube, r the radius of the tube, l its length, and v the volume of liquid delivered in the time t. If volume is in cubic centimeters, time is in seconds, and l and r are in centimeters, then η will be in poise.
- reflection c. (σ) a measure of the relative permeability of a particular membrane to a particular solute; calculated as the ratio of observed osmotic pressure to that calculated from van't Hoff law; also equal to 1 minus the ratio of the effective pore areas available to solute and to solvent.
- c. of relationship the probability that a gene present in one mate is also present in the other and is derived from the same source.
- reliability c. an index of the consistency of measurement often based on the correlation between scores obtained on the initial test and a retest (test-retest reliability) or between scores on two similar forms of the same test (equivalent-form reliability).
- respiratory c. SYN: respiratory quotient.
- Rideal-Walker c. a figure expressing the disinfecting power of any substance; it is obtained by dividing the figure indicating the degree of dilution of the disinfectant that kills a microorganism in a given time by that indicating the degree of dilution of phenol that kills the organism in the same space of time under similar conditions. SYN: hygienic laboratory c., phenol c..
- sedimentation c. (s) SYN: sedimentation constant.
- selection c. (s) the proportion of progeny or potential progeny not surviving to sexual maturity; usually defined artificially by expressing the fitness of a phenotype as a fraction of the mean or optimal fitness to give the relative fitness, and subtracting this fraction from unity. If the mean size of family in the population is 3.2 and that for a particular genotype is 2.4 then the fitness of the phenotype is 2.4/3.2 = 0.75 and the selection c. = 1 − 0.75 =.25.
- specific absorption c. (a) absorbance (of light) per unit path length (usually the centimeter) and per unit of mass concentration. Cf.:molar absorption c.. SYN: absorbancy index (1), absorptivity (1), extinction c., specific extinction.
- temperature c. the fractional change in any physical property per degree rise in temperature.
- c. of variation (CV) the ratio of the standard deviation to the mean.
- c. of viscosity the value of the force per unit area required to maintain a unit relative velocity between two parallel planes a unit distance apart.

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co·ef·fi·cient .kō-ə-'fish-ənt n a number that serves as a measure of some property (as of a substance) or characteristic (as of a device or process) and that is commonly used as a factor in computations <the \coefficient of expansion of a metal> see ABSORPTION COEFFICIENT

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co·ef·fi·cient (ko″ə-fishґənt) 1. a numerical factor multiplying a term in an algebraic equation. 2. a number preceding a formula in a chemical equation, indicating the relative number of molecules of that species entering the reaction. 3. a unitless constant characterizing a chemical or physical process. 4. a unitless statistical parameter indicating the amount of change in an outcome under given conditions.

Medical dictionary. 2011.

### Look at other dictionaries:

• coefficient — [ kɔefisjɑ̃ ] n. m. • déb. XVIIe; de co et efficient 1 ♦ Math. Nombre par lequel est multipliée une grandeur. Coefficient de proportionnalité. Valeur affectée d un coefficient. Chacun des nombres par lesquels sont multipliées les puissances de la …   Encyclopédie Universelle

• coefficient — of expansion coefficient of friction coefficient of rolling resistance aligning torque coefficient aligning stiffness coefficient braking force coefficient braking stiffness coefficient braking traction coefficient camber stiffness coefficient …   Mechanics glossary

• Coefficient — Co ef*fi cient, n. 1. That which unites in action with something else to produce the same effect. [1913 Webster] 2. [Cf. F. coefficient.] (Math.) A number or letter put before a letter or quantity, known or unknown, to show how many times the… …   The Collaborative International Dictionary of English

• coefficient — UK US /ˌkəʊɪˈfɪʃənt/ noun [C] ► in mathematics, a value that appears in front of and multiplies another value: »In 2x + 4y = 7, 2 is the coefficient of x. ► a number or a method of calculating a number that measures the characteristics of a… …   Financial and business terms

• Coëfficient — (lat.), jeder Ausdruck, in welchem nichts von dem, was als Hauptgröße in einem Gliede angesehen wird, vorkommt, u. womit diese Hauptgröße multiplicirt ist. Wo die letztere keinen C. hat, ist 1 als solcher anzusehen. Je nachdem in einem Gliede die …   Pierer's Universal-Lexikon

• coefficient — [kō΄ə fish′ənt] n. [ CO + EFFICIENT: orig. an adj. meaning “cooperating”] 1. a factor that contributes to produce a result 2. Math. a number or algebraic symbol prefixed as a multiplier to a variable or unknown quantity (Ex.: x in x(y+z),6 in… …   English World dictionary

• Coefficient — Co ef*fi cient, a. Co[ o]perating; acting together to produce an effect. {Co ef*fi cient*ly}, adv. [1913 Webster] …   The Collaborative International Dictionary of English

• Coëfficient — Coëfficient, in der Mathematik eine Größe, womit eine andere multiplicirt wird …   Herders Conversations-Lexikon

• coefficient — COEFFICIENT. s. m. Terme d Algèbre. On appelle ainsi Le nombre ou la quantité connue qui est au devant d une quantité algébrique, et qui la multiplie …   Dictionnaire de l'Académie Française 1798

• coefficient — also co efficient, 1660s (adj.), from CO (Cf. co ) + EFFICIENT (Cf. efficient). As a noun, from c.1600, probably influenced by Mod.L. coefficiens, which was used in mathematics in 16c., introduced by French mathematician François Viète (1540… …   Etymology dictionary

• coefficient — ► NOUN 1) Mathematics a quantity placed before and multiplying the variable in an algebraic expression (e.g. 4 in 4x2). 2) Physics a multiplier or factor that measures some property …   English terms dictionary