- 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.- 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.- 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.- 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.- 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.- 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..- 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.- 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).- 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..- 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 viscosity the 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.