correlation

In everyday conversation, people often use this word to describe a general link between two things. In science and math, it has a very specific meaning: it describes how two things move together, but it does NOT prove that one thing caused the other. This is why you often hear the phrase "correlation does not imply causation." It is most commonly used as an uncountable noun when referring to the general concept of a relationship, but can be countable when referring to specific statistical results.