The apostrophe is a tricky devil, arguably the trickiest bit of punctuation the English language offers. (And there are some doozies; semi-colons, anyone?) If you find yourself constantly second-guessing whether “its” or “it’s” is the correct word, you’re not alone. But fear not: the funny folks at The Oatmeal have made a handy chart that should dispel the confusion.

The chart is handy and comprehensive, but if you don’t want to print it off and tape it to your wall (which I did at the Ryerson Review of Journalism office, where I spend my days, because I am a complete punctuation nerd), here’s one thing to remember:

An apostrophe is a placeholder, generally speaking, and nothing more. If you’re not replacing a letter or a set of letters with an apostrophe, then you probably shouldn’t be using an apostrophe.

This is most clearly seen in contractions:

Do not becomes don’t, Should not becomes shouldn’t, that is becomes that’s, and so on.

But what about possessives, you ask?

Back in the day, possessives were denoted by adding es to the end of a word. So, “foxes” was both the plural and possessive of the word “fox.” Somewhere down the line, the powers that be decided this was far too confusing and began replacing the “e” with an apostrophe, thus the beginning of the use of an apostrophe-S to denote a possessive.

The fox’s home was filled with four baby foxes.

So there you have it. I hope that clears up your apostrophe confusion. For more of the fascinating history of the apostrophe, check out these posts from Grammar Girl and Word Detective.

(Image is a screen shot from The Oatmeal.)