Common Errors in English

[AChimp]

One thing that has failed to stick by me from my English classes is certain possessive terms. I keep forgetting whether or not, and when, I can use an apostrophe without an "s". Is it Max' or Max's? The Johnsons' or the Johnsons's?

Like pjalne said, you put just an apostrophe if you're using the plural possessive (or a contraction, but that's a totally different set of rules )

For example, I had more than one cat, I could steals the cats' ball, assuming the ball belonged to all the cats. If there was just one cat, I could steal the cat's ball.

It's Max's rather than Max' because there is just one Max. A common error is to assume that the S at the end of a proper noun implied plurality.

The plural possesive form would be Johnsons' only if the last name was Johnson... It's kinda hard to explain, so I will try to make up a few sentences for examples.

(Last name is Johnson)
The Johnsons have a nice car.
I got a ride in the Johnsons' car. (In this case, Johnsons' refers to the whole family)
I got a ride in Johnson's car. (Only one guy named Johnson).

(Last name is Johnsons)
The Johnsonses have a nice car. (Ooooh... plural!)
I got a ride in the Johnsons's car.