Apostrophes

Apostrophes (a word, incidentally, that sounds better when pronounced in French) are one of the most misused punctuation marks. The concept of possession (non-demonic, of course) seems to be a slippery one to convey.

Here's my attempt:

We associate items with one another using the concept of possession. You own a car. It's your car. I have a pen in my hand. It's my pen. Shannen Doherty has one eye that's a good two centimeters higher than the other. That's Shannen's eye.

We denote possession by the use of special words for pronouns (his, her, its) or by using an apostrophe and S for a specific noun: Will's site.

We also use apostrophes to denote missing letters in contractions.

Follow these guidelines for using apostrophes:

• Use apostrophes to indicate possession (even if the word ends in s!).
• Use an apostrophe after the S for plural possession.
• Use apostrophes to mark missing letters in contractions.
• Use apostrophes for plurals of letters, abbreviations, years, and other rare cases.
• Use it's to denote the contraction it is. Use its to denote possession.

Use apostrophes to indicate possession (even if the word ends in s!).

Apostrophes denote possesion:

I knew I was in trouble for crashing Dad's car.

There is some confusion about whether one should use the apostrophe for words that end in S. Although the rule is slowly changing as the standards of punctuation degrade inexorably into anarchy, most people still recognize that words ending in S still require an apostrophe and another S, like so:

Mr. Jones's crack pipe was still warm when we flushed him and his gang out of the shelter.

The reason to do this is because of the next rule:

Use an apostrophe after the S for plural possession.

When you have a word that is plural (and hence ends in S) that is also a possessive, place the apostrophe after the S.

The woodchucks' union never managed to organize past the first few meetings.

Make sure the word is plural. This enables readers to differentiate between several things possessing and one thing possessing that just happens to end in S.

Use apostrophes to mark missing letters in contractions.

A contraction is a handy shortcut combining two words into one that more accurately represents the way people speak:

We could not do that.

We couldn't do that.

Use apostrophes for plurals of letters, abbreviations, years, and other rare cases.

There are some cases where a plural would be confusing without an apostrophe.

Will all the students with D's please report to the execution chamber?

I remember back in the 1950's when it was expected for a man to drink three martinis before lunch.

Use it's to denote the contraction it is. Use its to denote possession.

This rule varies and will probably change over time, but at present it is considered correct to use the apostrophe only to denote the contraction instead of the possessive:

It's a sad day when I have to sell a bail bond to my own grandmother.

The ship hovered above us, its chromatic sheen glinting in the sun.

It's not a perfect solution, but it's the only way we have to differentiate the two.