- 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*.-(*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*.-a*correlation*c.*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.-the*diffusion*c.*mass*of*material*diffusing across a*unit**area*in*unit**time*under a*concentration**gradient*of unity. SYN:*diffusion*constant.-the*distribution*c.*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.-the percentage of a*extraction*c.*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*.-a*filtration*c.*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.-the*Hill*c.*slope*of the*line*in a*Hill**plot*; a*measure*of the*degree*of*cooperativity*. SYN:*Hill*constant.-SYN: Rideal-*hygienic**laboratory*c.*Walker*c..-**c. of**the*inbreeding**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*.-the amount of salts in the*isotonic*c.*blood**plasma*, or the amount that should be added to distilled*water*in*order*to prepare an*isotonic**solution*.-**c. of**the*kinship**probability*that two genes at the same*locus*, picked at*random*from each of two individuals, are identical by*descent*.-that*lethal*c.*concentration*of*disinfectant*that kills*bacteria*at 20–25°C in the shortest*period*of*time*.-that*linear**absorption*c.*fraction*of ionizing*radiation*absorbed in a*unit**thickness*of a*substance*or*tissue*. SEE ALSO:*absorption*c. (3). Cf.:attenuation.-(*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*.-**partition c.**SYN:*distribution*c..-a c. associated with*permeability*c.*simple**diffusion*through a*membrane*that is proportional to the partition c. and the*diffusion*c. and inversely proportional to*membrane**thickness*.-an*Poiseuille**viscosity*c.*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**the*relationship**probability*that a*gene**present*in one mate is also*present*in the other and is derived from the same source.-an*reliability*c.*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).-SYN:*respiratory*c.*respiratory*quotient.-**Rideal-**a*Walker*c.*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..-(*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.-**c. of**the*viscosity**value*of the*force*per*unit**area*required to maintain a*unit*relative*velocity*between two parallel planes a*unit**distance*apart.* * *

**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*** * *

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.*