[Modernman]

Exactly. If you're not invited by name, you don't attend, in my family.

We knew whether most of our single friends had a serious enough significant other to warrant inviting them. In case we didn't, we made sure to ask before sending out the invitations. Nobody got a "Mr. X and guest" but rather a "Mr X. and Ms. Y."

Of course, several of the significant others ended up being ex-significant others in the meantime.

[Tax-chick]

"Mr X. and Ms. Y."

I invited a couple of people to my wedding that way.

[nopardons]

And that is EXACTLY the way it should be done. Many thanks for the corroboration. :-)