The difference between its (possessive) and it’s (contraction) is grammar 101. It’s child’s play. It’s the ham sandwich of gourmet grammar. And yet it is one of the most common grammar errors, if not the most common error, out there in the world of very smart and savvy journalism students (and, don’t be fooled, professional journalists). But don’t feel too bad—there may be a reason why this particular mistake is plaguing your writing.

First things first:
Its is the possessive of the word it. The shark lost its prey when some tasty humans distracted it.
It’s is the contraction of it is or it has. It’s been a long time since there was a shark attack on the Jersey Shore.

I pride myself on being a bit of a grammar wizard (in training, perhaps), but every time I write the possessive of it without throwing in that apostrophe, I double back: it just feels wrong. Almost every other word is made possessive by adding the apostrophe-s, so why not it? I suspect this contradiction is the reason I see this egregious error cropping up so often (and the reason a couple of my professors have vowed to deduct a third of a letter grade for every its/it’s error found in a piece of writing).

Well, it turns out there’s a good reason for the confusion, but to fully understand its/it’s, we need to take a little trip through history.

Apostrophes first came into use around the 16th century, and were used primarily as a placeholder, generally in the matter of contractions. So, do not becomes don’t, that is becomes that’s and it is becomes ’tis (not it’s) and so on.

At the same time, a possessive is denoted by adding –es to the end of a word, meaning that sandwiches was both the plural and the possessive of the word sandwich. Needless to say, this is pretty confusing.

Around the 18th century, the grammar powers that be decide to start using an apostrophe to replace the e in the possessive form of words, thus the modern use of the apostrophe-s to denote a possessive. Now we’ve got sandwiches (plural) and sandwich’s (possessive).

So, now it’s is the possessive of the word it, and ’tis is the contraction of it is.

Confused yet?

Fast-forward a bit to the 19th century: the dawn of modern times (or something like that). The grammar gods decide that ’tis sounds way too archaic for their modern society, so the contraction is changed to it’s, and it’s up to the reader to decide whether the writer means the possessive or the contraction based on the context of the surrounding sentence.

This shouldn’t be too much of a problem because this is what we still do with proper nouns. Take the word Melissa’s for example: it is both the possessive of Melissa and the contraction of Melissa is or Melissa has. Melissa’s cat is named Apple. Melissa’s got a cat named Apple. See? Not so bad.

Well, the grammar gods, again, disagreed and decided that there needed to be some distinction between it’s (possessive) and it’s (contraction), so the apostrophe in the possessive form was dropped forever. (Sigh.) My research hasn’t produced the name of the individual responsible for this, but I think I’d like to give that person a stern talking to for causing me so much grief.

So there we have it: its is the possessive of the word it, and it’s is the contraction of the words it is or it has.

And the next time someone catches you in this mistake, you can relay this history lesson, and hopefully keep your third of a letter grade.

Quick tip: I’d wager my wizard hat that most of the its/it’s culprits know fully which word is which, and that most errors are unconscious typos. As such, you’re likely to pass over an error when proofing your work. Instead, open up the electronic copy of your story and do a search (control+F on a PC, command+F on a mac) for “ it” (note the space). This will pull up every instance of its or it’s in sequence and allow you to double-check you’ve used your words correctly in a few minutes flat.