Either way, you may already be well-versed in how to use the apostrophe, but here's a quick refresher on its usage.

The apostrophe can be used in three ways: to mark possession, to mark contraction, to mark the plural of single letters.

Most of the time, if you see an apostrophe hovering helpfully near a word, it's trying to mark possession or contraction.

First, let's look at how the apostrophe marks possession.

As you can see, the placement of this punctuation mark can really change the meaning of a sentence.

"Those robots in the sand are my sister's."

"Those robots in the sand are my sisters'."

"Those robots in the sand are my sisters."

When showing possession, the apostrophe belongs next to the noun that owns or possesses something.

The noun can be singular or plural.

Proper nouns work, too.

So if Lucy needs to get her robots under control before they cause mayhem, those dangerous creatures would be "Lucy's robots."

But what if Lucy was Lucas?

Would we write "Lucas' robots" or "Lucas's robots"?

And what if Lucas gave his robots to the Robinsons family?

Would it be "The Robinsons' robots," or "The Robinsons's robots"?

The truth is, even grammar nerds disagree on the right thing to do.

The use of 's after a proper noun ending in s is a style issue, not a hard and fast grammar rule.

It's a conundrum without a simple answer.

Professional writers solve this problem by learning what's considered correct for a publication, and doing that.

The important thing is to pick one style and stick with it throughout a piece of writing.

One more wrinkle.

Certain pronouns already have possession built in and don't need an apostrophe.

Remembering that will help you avoid one of the trickiest snags in English grammar: its vs. it's.

"It's" only take an apostrophe when it's a contraction for "it is" or "it has."

If you can replace "it's" with one of those two phrases, use the apostrophe.

If you're showing possession, leave it out.

Otherwise, contractions are pretty straightforward.

The apostrophe stands in for missing letters, and lets common phrases squash into a single word.

In rare cases, you can have a double contraction, though those generally aren't accepted in writing, with the exception of dialogue.

So it's possessive, it's often followed by s's, and it's sometimes tricky when it comes to its usage.

It's the apostrophe.