S's Rules (The Possessive in English)

People who only speak English often get hung up on the minor differences between the British "dialect" and the American "dialect" of the language. True, a few words are spelled differently and many words are pronounced differently, but communication is not a problem. When I lived in Europe, I was sometimes in a room with English speakers from half a dozen countries and we had no difficulty communicating- not even a little bit.

Compare that with the situation in some other language. People who speak other languages (in addition to English) know what I'm talking about. Sometimes the differences between dialects from city to city are so extreme that communication is difficult (if not impossible).

Therefore, it came as a surprise to me to find no clear, definitive rule about 's in the English language. Despite the absence of an Academie Anglaise, one can almost always find a clear consensus on the basic rules of grammar and usage. Occasionally, one will discover that a rule differs slightly between England and the States, but each side will have a single, clear rule. Not so with apostrophe s.

In school, I was taught the overly-simple rule that any word (whether singular or plural) than already ends with the letter s, simply appends an apostrophe to indicate the possessive. But, upon further digging, the rules (from both sides of the pond) seem to agree up to a point.

Let's see where the rules agree:

1. Any singular noun that doesn't end in "s" or an ess-sound appends an 's to make it possessive.

2. Any plural noun that doesn't end in "s" or an ess-sound appends an 's to make it possessive.

3. Plural nouns that end in "s" take only an apostrophe to indicate possession.

That, unfortunately is where the agreement ends. We're left with the final case: a singular noun ending in "s". Some sources indicate that proper nouns take only an apostrophe and all others take the full 's. Other sources say that only "historical" proper nouns use the apostrophe and all others take the full 's. Some sources even state the dubious rule that all singular nouns ending in "s" take the full 's.

The best rule (the one that most closely resembles current usage and (correct) historical usage) is the following:

4. A singular noun ending is "s" take either an apostrophe or the full 's depending on whether we pronounce the word with an added syllable or not.

For example, we say Chris-ess house (Chris's house). We pronounce the extra syllable, so we write the full 's.
But, we say Achilles- heel (Achilles' heel). We do not pronounce the extra syllable, so we write only an apostrophe.