In or Within?

Do you know when to use “in” and when to use “within”?

The difference can be subtle. I’ll give you the answer right away:

Use “in” if you are writing about a container.
Use “within” if you’re writing about a limit.

I should point out that “within” is more formal than “in,” too, and I generally advocate plain writing.

The limit can be any boundary, not necessarily physical. For example you might say “Get your room clean within the hour!”

The container doesn’t have to be physical, either. Here’s a quote from page 72 in an interesting book I’m reading, Listening In, by Susan Landau. (I’ll set aside mentioning that “located in” is redundant. “Located” isn’t necessary.):

Zero-day vulnerabilities are most prized when they work against widely deployed systems─and Stuxnet’s were all located in the Windows operating system, which made these particularly valuable.

As they deconstructed it, they began publishing their findings in blog posts.

Okay, here’s a comic with “in.” Try reading this and the sentences above with “within” and you’ll see why “within” doesn’t quite work.

Here’s an example of using “within” when “in” is better. Say it both ways:

These include the Schrödinger Basin, a relatively youthful crater within the larger South Pole–Aitken Basin, which is thought to be the moon’s oldest impact crater.

So here’s the rule: if you can use “in,” do so. Use “within” only when “in” sounds wrong. Most of the time “in” sounds right.