Correlation / Concordance / Accord / Link / Relation

Question

When I came across the word concordance, after I had looked up on a handful of dictionary I concluded that they have similar sense with the word accord and correlation but not synonym though.

But I would like to ask if I can rewrite a sentence which contains the word concordance in the following passage which I extracted from a tuition website.

Substantial evidence suggests that there is a genetically inherited predisposition to schizophrenia. For example, there is a concordance rate of about 48 percent for identical twins. The concordance rate for fraternal twins is considerably less, about 17 percent. Concordance rate refers to the percentage of both people in a pair having a certain trait or disorder. A person who has two parents with schizophrenia has about a 46 percent chance of developing schizophrenia. This probability is very high compared to the roughly 1 percent chance of developing schizophrenia in the general population.

The passage is already explaining what concordance rate means and I can see we cannot just replace the word concordance with the word correlation. Because I took statistics lectures before I don't think there is a term correlation rate but we can say correlation coefficient which is between -1 and 1. So I'll give a more simple example, for example I can say off the top of my head :

There is a correlation /link/ relation between crime and drug abuse.

Can we say :

There is a concordance / accord between crime and drug abuse.

So I need help more on the usage of the words concordance and accord in this sense.

Answer 1

Concordance is, in this case, a term of art in the field of genetics. See: http://en.wikipedia.org/wiki/Concordance_%28genetics%29

In more general usage, 'concordance' simply means 'agreement', as does 'accord'.

'Correlation' and 'link' imply a causal connection - in this case, that either crime causes drug abuse, drug abuse causes crime, or that both are caused by some third factor. Thus it would be inaccurate to use 'concordance' here.

Answer 2

In general, "concordance" does not mean the same thing as "correlation".

"Concordance" means "agreement". Like, "There is a concordance between Britain and France to ..." (do whatever).

"Accord" is similar to "concordance": an agreement. It is often used to describe join action, like, "All the parties agreed to proceed in accord with each other and with this plan." There's something of an idiom: "They were all in one accord", meaning, they all agreed.

"Correlation" means that two things tend to be associated with each other. It does not indicate agreement and is usually used when discussing events, rather than groups of people. So you might say, "There is a correlation between tobacco use and lung cancer."

I have to disagree with MrTheWalrus when he says that correlation means a causal relationship. It most definitely does not. There MIGHT be a causal relationship, but then again there might not. Indeed there's a common catchphrase in statistics: "Correlation does not prove causation", meaning, just because statistically A and B often occur together, that doesn't prove that A causes B. It may be that B causes A, or that both A and B are caused by some third factor C, or it may just be a coincidence.

"Link" and "relation" mean that there is some connection between the things, as opposed to just a coincidence. If you say, "There is a correlation between tobacco use and lung cancer", you are describing a statistic. If you say, "There is a link between tobacco use and lung cancer", you are saying that tobacco use causes lung cancer. It's not a coincidence, there's actually a cause and effect relationship. In context, there could be some other sort of relationship, not necessarily causal. Like you could say, "There's a link between Bob and Sally", meaning, they are doing something together or have something in common, not necessarily that Bob "caused" Sally.

As MrTheWalrus points out, "concordance" has a specific, technical meaning in genetics that is related to the common meaning but not the same. Note this is often done in English: people in some technical field take a word from general use and give it a specific meaning. (Do other languages do this? Never thought about that before.)

Side note: Every now and then someone learns such a technical meaning for a word and then says that people who use the word with the common meaning are being inaccurate, often ridiculing them for this supposed inaccuracy. To take a particularly silly example, when I was in school one of my teachers said that we were wrong to say that we were "doing a lot of work" in class, because "a physicist would say" that we were really doing very little "work" by the technical physics definition of work. Of course I'm sure that physicists routinely say they are "doing a lot of work" when they are staring blankly at a sheet of paper trying to interpret an experiment. No rational physicist is confused about the difference between "work" -- force expressed over distance and measured in joules -- and "work" -- effort expended to accomplish a task, which might be physical or mental.