homologue vs ortholog

[Lee Meisel]

Hi!

Recently when reading a variety of papers I have seen ortholog and
homologue used in similar context.  I'm pretty sure there is a
difference between ortholog and homologue but am unsure of what that
difference is.  Unfortunately, ortholog is not in the Webster's
dictionary or in a genetic dictionary we have available.  Could someone
please explain the difference between ortholog and homologue, as well as
the criteria necessary to define a sequence as an ortholog or a
homologue.  

I will post the responses if anyone else expresses an interest.

Thank you in advance.

Lee Meisel (meisel at aesop.rutgers.edu)
Eric Lam's Lab
AgBioTech
Rutgers University