I confess to being a spelling and grammar purist, but I hope not a troll. Most of the time I resist the temptation to point out the errors of others, but they still make me cringe. English is not an easy language, but there's one class of error that is so common yet so unnecessary, I'm willing to risk a diary about it. I'm talking about the misuse of the apostrophe.
There is only one thing you need to remember to never misuse the apostrophe again:
One Simple Rule
The purpose of the apostrophe is to indicate that part of a word missing. Period.
That's all you need to know. Well, there is one teeny-tiny exception, but that's easy to remember too.
Simple Contractions
Example 1: That's all you need to know.
Example one is actually saying "That is all you need to know." The "i" (and the space, if you want to be picky) are missing, so there's an apostrophe. Simple, no? Other common examples: can not = can't; you are = you're; they will = they'll. The struck-out letters are left out, which is why you need an apostrophe. Using the apostrophe is important not just for nitpicky correctness, but to avoid confusion; there's a big difference between "we are" and "were", and between "he will" and "hell".
Also note "they are = "they're". This word is a problem for some people because there are two other common words that are pronounced the same. "There", meaning "in that place", is spelled the same as "here" (in this place), only with a "t" in front. The other word, "their" (the weird one), means "belonging to them." If these words are a problem for you, check yourself by starting with the One Simple Rule: Do I mean "they are"? Then you want the one with the apostrophe because the "a" is missing. Do I mean "here or there"? Then use the one that's spelled like "here". Otherwise, the only thing left is "their".
The same goes for "you're" and "your". If you mean "you are", write "you're". The word that means "belonging to you" has no missing letters, so no apostrophe (and no "e").
The Dreaded Letter "S",
Most people understand the use of apostrophes in simple contractions. They get into trouble when the part of the contracted word that isn't left out is an "s". This is because a final "s" is used for several different purposes. Sometimes the apostrophe goes before the last "s", sometimes after. Sometimes you add another "s", sometimes you don't. And sometimes, this confusion results in people using an apostrophe when they shouldn't. This is where the One Simple Rule will help you.
Plurals
In English we add an "s" (most of the time) when we're talking about more than one object. One book, two books. One box, two boxes. Well, there are no letters missing in "two books", so there's no apostrophe. Simple!
Note that this applies to abbreviations and acronyms too. Two television sets = "two TVs", not "two TV's". "Wait, wait!" I can hear you say, "the letters 'ision' are missing, so you do need an apostrophe". If you want to play that game, you'd have to write "two T'V's" (the letters "ele" are missing too), and that just looks silly. You certainly don't put two apostrophes in "one T'V'", do you?. Leave 'em both out!
Possessives
Example 2: John's book is interesting.
What is going on here? The writer does not mean to say, "John is book is interesting." OK, here's where I'm going to distort history a bit in order to make things easier to remember. (For those who are sticklers for accuracy, the apostrophe-s ending of possessives is the remnant of the "-es" ending of masculine singular nouns declined in the genitive case, from the days when English was much more highly inflected than it is now, but this way is easier to remember.)
Centuries ago, it used to be the fashion for people to write their names in their books and then add "His Book" (or "Booke". You think spelling is weird nowadays!) So if your name were John Smith, you might write
John Smith
His Book
So "John Smith his book" = "John Smith's book"
And yes, although it may seem sexist nowadays, "Mary Smith his book" = "Mary Smith's book". Remember, I'm not trying to be historically accurate, I'm trying to make this easy to remember.
So remember this: If the sense of the sentence is such that you could use "his" in this Olde Englishe way, you need the apostrophe-s to indicate "his".
Already Ends in "S"
So what do you do with the possessive apostrophe-s when the word already ends in "s"? Here the "s" sometimes gets left off because it sounds weird, but you still need the apostrophe. "Murray Waas's column" sounds OK, but "Democrats's agenda" sounds doofy, so the final "s" gets left off, but you still need the apostrophe. Sometimes either way sounds OK, so it's up to you if you want to say "Jesus' teaching" or "Jesus's teaching". Either is OK; you decide which you like better.
I once saw a grocery store in a Hispanic neighborhood whose sign read "Gome's Grocery". I could be wrong, but I'm betting the owner's name was "Gomes", not "Gome". If so, the sign should have read "Gomes' Grocery". Or "Gomes's".
Hypercorrection
Sometimes people who have been penalized for leaving out apostrophes, but who haven't had the One Simple Rule properly explained to them are so afraid of making a mistake that they hypercorrect; that is, in "correcting" something that was right to begin with, they make an error. "Democrat's rock!" is wrong; there are no missing letters (Democrat is rock? Democrat has rock? Doesn't make sense!) On the other hand, there is an apostrophe in the possessive: "a Democrat his agenda" = "a Democrat's agenda". In the phrase "Congressional Democrats' agenda"; the "s" shows you're talking about more than one Democrat, the apostrophe shows the Olde Englishe "hi" from "his" is missing; and the "s" from "his" is missing too, 'cause it would sound weird if it were there.
The Bottom Line
If you're ever puzzled about whether you need an apostrophe or not, try rewriting the sentence as fully as possible. If there's part of a word (not forgetting the Olde Englishe "his") which is missing in the original, use an apostrophe. Otherwise, don't. Simple!
The One Teeny-Tiny Exception
It might seem that the possessive form of "it" ought to have an apostrophe-s, but it doesn't. There is no apostrophe in "his" or "hers" (as in "That idea wasn't mine, it was hers."), so there's no apostrophe in "its" either. You do use an apostrophe when you mean "it is" or "it has". But not when you're saying "it his book. The Olde Englishe bit doesn't apply in this case, just as it doesn't apply in the case of "his book" (not "hi's book").
So the One Teeny-Tiny Exception is: Use the apostrophe-s when you mean "it is" or "it has", only. In the sentence "It's got its running shoes on," the first part = It has got", so you use the apostrophe. In the second part, even though the Olde Englishe "his" bit applies, don't use the apostrophe. That's the one teeny-tiny exception.
I hope this diary has helped any of you who might have been confused about apostrophes. Just remember, use an apostrophe if something is left out, otherwise don't. It's simple!