An oft-forgotten AP style rule calls for singular common nouns that end in s (bus, business, campus, etc.) to be made possessive by adding an 's instead of just an apostrophe (bus's, business's, campus's, etc.). It catches people off guard because they're so used to adding just an apostrophe when a word ends in s. But it makes sense when you consider that the s is pronounced, which seems to be the guide AP used in developing these rules.

I was caught off guard tonight, however, with the word corps. Not only does it seem strange to just add an apostrophe because of the rule above; but because it has no sibilant ending, the 's seems necessary.

But then there's another rule for nouns the same in singular and plural (corps, deer, moose). AP says, "Treat them the same as plurals, even if the meaning is singular."

Sigh.

While we're on the subject of possessives, though, what's up with this rule?

SPECIAL EXPRESSIONS: The following exceptions to the general rule for words not ending in s apply to words that end in an s sound and are followed by a word that begins with s: for appearance' sake, for conscience' sake, for goodness' sake.

First of all, it needs to be rewritten: Goodness does end in s. Second, it doesn't hold true. Race' start? No way; it's race's start, even though race ends in an s sound and is followed by a word that begins with s.

So what about inheritance' stipulation? You got me; I have no idea how I would pronounce that. And that's the problem of these rules.