The Most Annoying Mistakes in Grammar: It's and Its

The apostrophe is a much-loved element of punctuation. People want to throw this little fellow around with wild abandon. However, the Grammar Grouch is most annoyed with writers who are not aware of the difference between "it's" with an apostrophe and "its" without an apostrophe.

The Apostrophe's Mission in Life

The apostrophe: It's useful because it lets you, dear writer, omit letters, which saves time, words, ink and space, allowing you to contract two words into one. Yet its use is also very possessive in some cases, letting you know right up front who owns what. Why then are so many mistakes made in the use or omission of an apostrophe in the words "its" or "it's"? Many otherwise passable writers fall further into mediocrity and hopeless error because of the it's/its quandary and its subsequent misuse. It's a shame, isn't it?

What It's Means

"It's" with an apostrophe is a contraction. Although you have used the apostrophe to represent possession all your literate life, you must not do so in this case. You must only use the apostrophe to designate letters you are omitting. When you could say "it is" but have the intent of being informal and breezy, you omit the second "i" and replace it with an apostrophe. It is=it's. Similarly "it isn't" has an apostrophe to show the omission of the letter "o" in "not." Is not=isn't.

There are countless examples, so don't bother counting them: Wasn't for was not. Won't for will not. Aren't for are not. Can't for cannot.

An Irritating Habit of Haphazard Writers

Although we are concentrating here on the irritating habit haphazard writers have of mixing up it's and its, there are other words exhibiting the same principle that don't seem to be a problem. For cryin' out loud, you can remember to use an apostrophe when you write "I'm" instead of "I am" can't you? Or, you're for you are. They're for they are. He's and she's for he is and she is. In every case, the apostrophe represents a missing letter and space. So why on earth should there be a problem with it's for it is?

Well that's (that is) enough about it's (it is). Please don't (do not) forget this and incorrectly use "it's" and thus irritate your readers, not to mention the Grammar Grouch. Repeat after me: It's meaning it is uses an apostrophe to represent the missing "i".

Why Is "Its" Such a Darn Possessive Pronoun?

Writers, poor things, clack merrily along on their keyboards writing about Melinda's pencil, Alice's schedule, Marvin's acne, Junior's diaper or Victoria's Secret, fully confident that every apostrophe correctly indicates possession. But when the maple tree loses its leaves, this same writer often stumbles, yearning to add the familiar apostrophe. However, as we discussed above, the apostrophe is already serving in a contraction and is simply not available to show possession here, so get over its. Repeat after the Grammar Grouch: Its = possession.

But Doesn't the Apostrophe Always Denote Possession? (No, Not In Its Case.)

Accept it. You must write "its leaves are falling " without your dear apostrophe. If your apostrophe finger is itching to be used, you must write "the maple tree's leaves are falling." Because yes, the apostrophe does denote possession in a singular noun. The apple's flavor. The dog's breath.(Ewww.) It's true even with nouns that already have s's! It's (it is) the assistant's job, but it's the boss's problem. Don't try to keep up with the Jones's lifestyle.

Don't Plural Possessives Ending in "S" Need an Apostrophe?

Yes,they do require an apostrophe, although plural possessives already ending in "s" do not need yet another "s." The bosses' problems are worse than all the assistants' problems put together. The roses' petals, the girls' room, the boys' clubhouse.

How About a Plural Noun with No "S?"

If you have a plural noun that does not end in "s" you may happily add one, along with your beloved apostrophe, when you go to the men's room. Or mention the children's bedtime.

Grammar Grouch Says, "Get Your It's and Its Straight!"

If only you will use your it's and your its accurately, the Grammar Grouch promises not to report you to the Apostrophe Police.

Sources:
Personal grouchiness
http://grammar.about.com/od/punctuationandmechanics/tp/GuideApostrophe.htm

Disclaimer: The Grammar Grouch is not perfect, and has been known to have a rare grammar glitch, just not the one being grouched about. (See right there, a dangling participle.)