Correlation is something that scientists are often trying to show––is there a correlation between smoking and poor health or between napping and productivity? How about daily flossing and good grades?
Correlation derives from the Latin cor- 'together' and -relatio 'relation'––the word is all about things that go together. But beware: just because a study shows a correlation between two variables, it doesn't mean one necessarily causes the other. There is a significant correlation between going to high school and being a teenager, but that doesn't mean that going to high school causes you to be a teenager.