# Describing a relationship that is related via a third party?

How do you describe something where

A does not cause B,

but

C causes A and B.

What would you call the relationship between C and A/B and the relationship between A and B? I'm sure there's some logical terminology for this.

Thanks.

• Do you mean that since c causes a and b, there might be a confusion among the observers that 'a' has some role to play in causing 'b'? Dec 27, 2015 at 15:24
• @JonyAgarwal yes exactly. Dec 27, 2015 at 16:16
• You should try this question in MathOverflow or Theoretical Computer Science SE sites! Dec 27, 2015 at 16:32

In phsycology we call variables that correlate covariants, thus saying they vary together but not necessarily cause each other.

From M-W:

Covariant: varying with something else so as to preserve certain mathematical interrelations

This doesn't necessarily mean there's a common cause to both of them (c is causing both a and b), but it conveys the idea that, even though a and b are related, they aren't necessarily a cause for one another.

Also see Third-cause fallacy

Another word is confounded, although this one is pretty much restricted to Statistics and may have negative connotations. From the wikipedia:

"We say that X and Y are confounded by some other variable Z whenever Z is a cause of both X and Y."

We could call the relation between A and B to be coincidental/correlated and the one between C and A/B to be causal relationship. I would suggest you to look into Correlation does not imply causation to not just get some more insight into the subject matter but also the relationship label.