Correlation (noun)

1. A mutual relationship or connection between two or more things.
2. A statistical association between two variables.
3. The extent to which two or more things are related or similar.

Origin:

From late latin correlatio, from latin correlat-, past participle of correlare ("to bring together, connect"), from co- ("together") + relare ("to bring bac.k")

Examples:

1. There is a positive correlation between education and income.
2. There is a correlation between the increase in temperature and global warming.
3. There is a high correlation between the results of the two tests.
4. The correlation between crime and poverty is well-established.
5. The correlation between the two stocks is not strong.