Become an apostrophe wizard

People get confused by apostrophes but it is really quite straightforward. Here's a handy guide:

The rules, in brief:

No apostrophe for a simple plural or a verb ending - "two Johns", "John runs"
Apostrophe before the "s" for belonging to one thing or person - "John's book"
Apostrophe after the "s" for belonging to more than one - The two Johns' laughter
An apostrophe when something is missing, "Let's go", "Isn't it?" "It's" (meaning "it is")
No apostrophe for "its" (meaning "belonging to it").

Explanation

People first used apostrophes (') in English to show that something is missing:

"Let's go to the pub."

Here "let's" is short for "let us". The apostrophe shows there is a missing "u".

"I wouldn't if I were you." – here the apostrophe shows an "o" is missing ("I would not.")

"It's a nice day" – here the apostrophe shows the "i" is missing from "it is".

So far, so good.

In Old English, people used to use "his" to show when something belonged to someone.

"John, his house" was shortened to "Johnis house" and eventually to "John's house". The apostrophe was there to show that "his" or "is" was missing. It's still useful to keep it because we also add "-s" to words to show the plural (when there is more than one). The apostrophe helps us to know when the "-s" means possession, not plural, as in:

"There are two Johns in the class. The first John is the other John's cousin"

But what happens when you get a plural and possession coming together? To indicate both, we put the apostrophe after the "-s":

"The sound of the two Johns' laughter filled the room."

If there is nothing missing and the "-s" just shows there is more than one of something, you don't need any apostrophes.

There is one problem - and this is where most people get confused:

How do you distinguish between "its" meaning "belonging to it" and "it's" meaning "it is"?.

Well, you can see for yourself. If it means "it is" you keep the apostrophe. If it means "belonging to it" you just put "its".

Finally, you sometimes get an "s" at the end of a verb as in "Dad lets me stay out till ten." There's nothing missing here, so no apostrophe needed.

So, to summarise again:

No apostrophe for a simple plural or a verb ending - "two Johns", "John runs"
Apostrophe before the "s" for belonging to one thing or person - "John's book"
Apostrophe after the "s" for belonging to more than one - The two Johns' laughter
An apostrophe when something is missing, "Let's go", "Isn't it?" "It's" (meaning "it is")
No apostrophe for "its" (meaning "belonging to it").