1. mutual or complementary relationship: a relationship in which two or more things are mutual or complementary, or one thing is caused by another the close correlation between the two factors
2. act of correlating: the act of correlating, or the condition of being correlated
3. statistics relatedness of variables: the degree to which two or more variables are related and change together
[Mid-16th century. < medieval Latin correlation- "mutual relationship" < Latin relation- (see relation)]