correlation

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. A causal, complementary, parallel, or reciprocal relationship, especially a structural, functional, or qualitative correspondence between two comparable entities: a correlation between drug abuse and crime.
2. n. Statistics The simultaneous change in value of two numerically valued random variables: the positive correlation between cigarette smoking and the incidence of lung cancer; the negative correlation between age and normal vision.
3. n. An act of correlating or the condition of being correlated.

Century Dictionary and Cyclopedia

1. n. Reciprocal relation; interdependence or interconnection.
2. n. The act of bringing into orderly connection or reciprocal relation.
3. n. In physiology, specifically, the interdependence of organs or functions; the reciprocal relations of organs.
4. n. In geometry, such a relation between two planes that to each intersection of lines in either there corresponds in the other a line of junction between points corresponding to the intersecting lines in the first plane; also, a relation between two spaces such that to every point in either there corresponds a plane in the other, three planes in either intersecting in a point corresponding to the plane of the three points in the other space to which the three intersecting planes correspond; more generally, a relation between figures, propositions, etc., derivable from one another in an n-dimensional space by interchanging points with (n—1) -dimensional flats.
5. n. In statistics, the relation of two or more variable quantities. One variable quantity never determines another completely. For instance, in a certain biological type size never completely determines weight, although large individuals are, on the whole, heavy. The values of one variable, which are correlated with a certain value of another variable, are called an array. When the variability is normal, the average deviation of the array is equal to the deviation of the correlated measure multiplied by a constant which is called the coefficient of regression. A comparison of the coefficients of regression of the first variable considered as a series of arrays of the second, and of the second considered as a series of arrays of the first, leads to their reduction to a common coefficient of correlation which equals the average of the products of all the correlated pairs of deviations, divided by the product of their standard or mean square variabilities. The variabilities of the arrays are equal to the variability of each complete series multiplied by √— r where r is the coefficient of correlation.

Wiktionary

1. n. A reciprocal, parallel or complementary relationship between two or more comparable objects
2. n. statistics One of the several measures of the linear statistical relationship between two random variables, indicating both the strength and direction of the relationship.

GNU Webster's 1913

1. n. Reciprocal relation; corresponding similarity or parallelism of relation or law; capacity of being converted into, or of giving place to, one another, under certain conditions.

WordNet 3.0

1. n. a reciprocal relation between two or more things
2. n. a statistic representing how closely two variables co-vary; it can vary from -1 (perfect negative correlation) through 0 (no correlation) to +1 (perfect positive correlation)
3. n. a statistical relation between two or more variables such that systematic changes in the value of one variable are accompanied by systematic changes in the other