[pat_shaughnessy]

Thanks Gary... yea and all of these things more or less mean the same thing.

At a more technical, detailed level, however, the Ruby core team uses both the term "metaclass" (in the same sense Smalltalk uses it - the class of a class), and the term "singleton" (the hidden class of a single object instance). You can see what I mean by looking through the MRI class.c source file.

[gwright]

Yep and that was one of the reasons that the naming confusion persisted for so long.

[chc]

Also one of the reasons it's a little bit annoying that they picked a term that already had a different meaning not only within the wider context of programming in general, but within their own language.