It's July 4th, and I'm doing a teaching post??? So be it.
I think this'll be an easy one. (Maybe, if I do my job right.) I did a post on what is, in my opinion, one of the most common mistakes made world-wide among those who speak and write English, "Its" vs. "It's", a short while back. Hope it was helpful.
Without trying to identify each word's ultimate modifications and obscure definitions, I am going to try and simplify it for you. (And, unless you are going on to get an advanced degree in English -- or maybe, worse yet, having to exactly define what the word 'there' means for a totally exasperating English teacher -- this little mini-lesson should serve you well for many many years!)
Let's begin with "they're".
First of all, the apostrophy should be a pretty good-sized clue. An apostrophy is used to either 1) indicate that a letter (or letters) is (are) missing or 2) to indicate possession.
To indicate possession, one would expect to see an "s" somewhere. "Helen's", "Tammy's", Katie's", "Jim's" ... all indicating something that belongs to 'Helen', 'Tammy', 'Katie', 'Jim'.
What about the case where 'it' belongs to more than one person?? Let's say, for example, that it is the "family's". What does THAT mean? (Close your eyes, and don't look at the answer, OK?) What was the word that appeared before the apostrophe? Family, meaning that whatever 'it' is belongs to the whole family. What about this example, that it is the "families'". NOW what? Again, look at the word that appeared before the apostrophe. NOW, whatever 'it' is belongs to all of the families, not just one. (This was probably not the best example!)
Let's try something else, the families' church. In other words, a church originated by and belonging to all of the families. (Might be a little better example, but not much.)
"They're" ... I don't see anything there to indicate possession. What I DO see (before the apostrophe) is the word 'they'. What the devil could "'re" mean? Well, I just can't think of anything close except the word 'are'. And "Eureka", I have it ... it's a contraction! The apostrophe indicates the missing letter 'a'. So, "they're" = "they are".
[By the way, I don't think I'm doing exceptionally well here in the teaching department, but I'll slog on forward, OK? Try and bear with me.)
"Their" is a pronoun ... plural, and indicating possession. VERY similar to 'it' in that it requires no apostrophe to indicate same.
OK. Let's look at some examples. What's the plural of he? (Answer the question before you look at the answer, would you?) They. She? They. I? We. It? Its. (Remember my lesson?? Or 'they'. Either will do.)
When you get into possessives, there are seemingly just a 'ton' of exceptions, which make our common language all the more difficult to master.
What if something belongs to 'he'? You don't say he's, you say his. If it belongs to 'she', you say hers. (Notice that there is no apostrophe on either of the preceding.) If it belongs to 'they', you say their or theirs. If something belongs to 'it', you say its. (Again, no apostrophe.)
It's so simple, isn't it? Pronoun possessives do not have an apostrophe! (How the devil did I ever get into all this in the first place? I mean, I ask you!)
Now that I've thoroughly and completely confused and discombobulated you, I will end this by saying that "there" belongs to every other use.
Is that a 'copout' or what? (Yeah, it's a copout. I'm trying to end this post so that I can take a shower, wash my hair, and drive down to Pearland to spend some time with my friends on the 4th.)
Hope all y'all have/had a great one, and come back at me with your comments/consternations/questions/whatevers, OK?
PS ... It's now a little after 10pm, and I just got back home. I'm in the world's best mood. After eating outside and visiting down there in Pearland, I took a little nap before driving back. I stopped a couple of times along the way to watch fireworks, and then tuned the radio in to PBS to accompany me on the tollway, and guess what was on??? They were broadcasting the symphony performance live from Miller Theater, concluding with the "1812", cannonfire and all!!!! Can you believe it?? I'm just grinning from ear to ear. Man oh man, what a perfect way to end the evening.
Listen, people, I'll come back and look at this post again tomorrow and see if I can't fix some of the 'lesson' so it's more understandable. Am pretty sure I made a mess of it. But, tomorrow is another day, right? See you then.