Apostrophes with possessive nouns are all about location, location, location. For example:
Those are the boy's sleeping bags.
Those are the boys' sleeping bags.
These two sentences may look identical at first, but a closer inspection reveals that the slight change in location of the apostrophe completely changes the sentence. In the first sentence, there are multiple sleeping bags that belong to one boy. In the second sentence, the sleeping bags belong to multiple boys. How can you tell? Simply look at the word before the apostrophe. In the first sentence, you see "boy," so you know there is just one boy. In the second sentence, you see "boys," so you know there are several boys. In most cases, plural possessives end in "-s'," since most nouns are made plural by adding an s; however, with plural words not ending in an s, like "people" and "children," simply follow the traditional "-'s" rule.
One of the most heated debates in English is whether singular nouns ending in s should have "-'s" at the end or just an apostrophe in order to make it plural. Personally, I've always been a fan of "-'s" since they are singular nouns. However, I recently came across the AP (Associated Press) Style rule for this situation: use "-'s" if the following word does not start with an s. For example:
That is Chris's hat.
Those are Chris' socks.
To give you an idea of what I mean, let's take a look at a commonly misspelled shortened word. When people are too lazy to write out "until," they drop the first two letters. Some write "till," and some write "til'," but both are wrong. Knowing the true function of the apostrophe, it becomes clear that the proper way to spell it would be as "'til," where the apostrophe acts as a replacement for the "un" in "until."
Determine whether the italicized word is correct with regards to the parenthetical clarification. If it is not correct, fix it accordingly.
1. I am going to the girls house today. (The house of several girls)
2. Do you like the hostess' nose? (The nose of the hostess)
3. I cannot wait until I get to have shakes n' floats! (Shortened word for "and")
4. The dentists' office is dreary. (The office of one dentist)
5. I want to see peoples' reactions! (The reactions of people)
Quiz! Answers: 1. Girls' 2. Hostess's 3. 'n' 4. Dentist's 5. People's