What is the definition of correlation and coupling?

[lsloneil]

When dealing with system containing millions of particles( for example, charged particles or magnetic particles) with statistical mechanics, I may often see the description or explanation that the certain effect is due to the coupling or correlation of particles. So can anybody give me a specific definition of coupling and correlation? Does coupling or correlation simply mean the interaction between particles?

Thanks a lot!

 

[pam]

Coupling means interaction.
Correlation can occur because of symmetries without explicit interaction.