Unfortunate fact: Grammar and style books don’t agree about apostrophe use. Even the simplest apostrophe rule is the subject of controversy:

Add an apostrophe and an s to show possession of singular nouns.

I followed up on the client’s request.

I stepped on the boss’s foot.

Some grammar books grant an exception if adding an apostrophe and an s to a name ending in s creates an awkward pronunciation:

Sophocles’ works were required reading in college.

Illinois’ current business climate will affect our decision.

To make it more confusing, the Associated Press style book contradicts what you were taught in school and says to add only the apostrophe to any proper name ending in s. However, this leads to awkward and unrealistic pronunciations:

I borrowed Agnes’ employee manual.

I studied Elvis’ life.

Our company will be affected by Congress’ latest bill.

So unless you’re writing for the Associated Press, use the apostrophe and the s if you would pronounce the extra s in a name.

The Associated Press also has an odd rule saying that even for singular common nouns ending in s, you should add only the apostrophe if the subsequent word begins in s:

I stepped on the boss’s foot.

I stepped on the boss’ stiletto heel.

The New York Times Manual of Style and Usage is more relaxed: unlike the AP manual, it says to use the apostrophe and s for proper names ending in s. However, it offers an exception for names ending in a sibilant sound that follows a vowel and another sibilant. Sounds complicated, but it refers to simple words like Kansas, Texas, and Moses.

Why should you care about the journalism rules if you’re not a journalist? The news stories you read each day in newspapers and magazines or on the Internet are edited according to these alternate punctuation rules, so they may have affected your apostrophe use. Also, maybe your workplace writing includes press releases. So knowing the purpose and audience for your piece of writing is important.

The apostrophe rules for plural nouns — nouns referring to more than one item – are largely undisputed:

Add only an apostrophe to plural words ending in s.

He was docked eight weeks’ pay.

The three agents’ sales for August totaled $8 million.

Add an apostrophe and an s to plural words not ending in s.

The publishing house is adding children’s books to its line.

It’s a real problem

The most common apostrophe problem arises around the word it. The word is a solid, everyday pronoun, so it seems natural to add an apostrophe and an s to make it possessive. “Wrong!” your English teacher screams. Don’t worry — you’re not stupid. It makes perfect sense to add an apostrophe and s just as you would to any other word. However, it’s wrong because its has been corralled into the group of possessive pronouns by a sadistic grammarian.

To understand this tricky word, it’s important to understand that the apostrophe is used to show possession in words that are not usually possessive. For example, a computer is a thing, so the word computer is a noun. But sometimes the word isn’t serving its normal function of being a noun: it is acting as a describing word showing possession:

My computer’s constant beeping drove my coworkers crazy.

In that sentence, beeping is the noun, and computer’s is a describing word. The apostrophe signals to the reader that the word is being used in a different way than expected.

But certain words exist in our language solely to show possession: his, hers, theirs, ours, its. So they don’t need an apostrophe because their usage isn’t changing.

Two easy ways to remember how to do it right:

If you write it’s, you mean it is. Always. Picture its with other possessive pronouns: his, hers, theirs, ours. You wouldn’t write hi’s or her’s. So keep the apostrophe out of its as a possessive word, even if you think it’s stupid.

More controversy

Disagreement also arises about using an apostrophe for plurals of letters, numbers, abbreviations, and words used as words. Here’s a rundown:

MOST GRAMMAR BOOKS (not all agree)

Add an apostrophe and an s to show the plural of words used as words, letters used as letters, numbers used as numbers, and acronyms/abbreviations. But use only the s for plurals of decades:

The accountant accidentally added some extra 2‘s to the budget total.

Our company earned two B‘s and an A on its marketing scorecard.

You used too many and‘s at the beginning of your sentences in this report.

Mail out the DVD’s on our new product line immediately.

We haven’t updated the company logo since the 1990s.

ASSOCIATED PRESS

Add an apostrophe and an s to show the plural of single letters used as letters. But use only the s to show plurals of numbers used as numbers, acronyms/abbreviations, words used as words and the plurals of decades:

The accountant accidentally added some extra 2s to the budget total. Our company earned two B‘s and an A on its marketing scorecard. You used too many ands at the beginning of your sentences in this report. Mail out the DVDs on our new product line immediately. We haven’t updated the company logo since the 1990s.

NEW YORK TIMES

Add an apostrophe and an s to show the plural of letters used as letters, numbers used as numbers, acronyms/abbreviations, and the plural of decades. But use only the s for words used as words: The accountant accidentally added some extra 2‘s to the budget total. Our company earned two B ‘s and an A on its marketing scorecard. You used too many ands at the beginning of your sentences in this report. Mail out the DVD’s on our new product line immediately. We haven’t updated the company logo since the 1990’s.

MODERN LANGUAGE ASSOCIATION (MLA style is used for academic writing in the humanities)

Add an apostrophe and an s to show the plural of letters used as letters. But use only the s for numbers used as numbers, acronyms/abbreviations, and the plural of decades. No specific rule is given for words used as words, but there’s a strong indication to omit the apostrophe:

The accountant accidentally added some extra 2s to the budget total. Our company earned two B‘s and an A on its marketing scorecard. You used too many ands at the beginning of your sentences in this report. Mail out the DVDs on our new product line immediately. We haven’t updated the company logo since the 1990s.

CHICAGO MANUAL OF STYLE (used in the publishing industry and certain academic applications)

Use an apostrophe and an s to form the plural of lowercase letters used as letters and abbreviations containing periods. Use only the s for capital letters used as letters, numbers used as numbers, and the plurals of decades. Also use only the s for words used as words, with possible exceptions for such examples that are awkward or in quotation marks:

The accountant accidentally added some extra 2s to the budget total. Our company earned two Bs and an A on its marketing scorecard. (Exception: Mind your p’s and q’s.) You used too many ands at the beginning of your sentences in this report. Mail out the DVDs on our new product line immediately. (Exception: Even three Ph.D’s couldn’t solve the problem.) We haven’t updated the company logo since the 1990s.

Confused? You should be. Each set of rules is slightly different. Find out the accepted style in your workplace.*

Next time: Quarrelsome Quotation Marks

Interesting related links

A fun blog that posts examples of misused apostrophes:

http://www.apostropheabuse.com/

An article about the struggle over its vs it’s:

http://www.newsweek.com/1995/11/05/its-academic-or-is-it.html

An article about how punctuation is being lost in the new age of texting:

http://www.newsweek.com/2008/08/01/the-death-of-english-lol.html

A story about how Arkansas struggled with apostrophe use with its name, proposing a bill that became law:

http://www.boston.com/news/nation/articles/2007/02/27/arkansas_house_to_argue_over_apostrophes/

*Special note: Words used as words, numbers used as numbers, and letters used as letters are usually italicized but not in boldface. However, for purposes of drawing attention to words used as words in my blog, I have chosen to add the boldface.