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First of all, what is a personal pronoun? A pronoun is a word that stands in place of a noun. So instead of saying "Gordon" you can say "he". And instead of using your full name every time you talk or write about yourself, which would sound rather odd, you can use "me", "myself" or "I".
There are three sorts of personal pronouns, depending on what the person being talked about is doing.
Subject Personal Pronouns are: I, you, he, she, it, we, and they. They are used when the person being talked about is performing the actions, and causing things to happen. They are the subject of the sentence. For example: I drove the car. She ate jelly snakes. They were scared of the squirrels.
Object Personal Pronouns are: me, you, him, her, it, us, and them. These pronouns are used when the person being discussed is the object of the sentence, and they are affected by the actions. For example: The ducks were too loud for me. Gordon took her to the party. Please help us with the cleaning up!
Reflexive Pronouns are: myself, oneself, himself, herself, itself, yourself, ourselves, yourselves, and themselves. They are always the object of a sentence (ie having something done to it). Generally reflexive pronouns are used to add emphasis — "I cooked the banquet myself!" Adding "myself" to the sentence emphasises that you're proud of what you've done (and rightly so!).
Generally we use "myself" in sentences where you've already used "I". "While Troy loves them, I'm not fond of jelly snakes, myself." It is correct to say "This is a photo of myself", too. "Myself" emphasises your role in the sentence.
Now, generally it's not too hard to know which pronoun to use, especially if English is your native tongue. But it gets confusing when we add a second person into the mix, and this trips up many people, including native English speakers. I've often seen things such as "A photo of Dad and I" or "Mum and me are going to the beach" (both of which are wrong).
So what's the neat little trick I've got for you? It's this:
Figure out the correct sentence for yourself alone, and then add in the second person without changing your pronoun.
So "I went to the beach" is correct, and becomes "Tom and I went to the beach" when you go with your friend.
"A photo of me" is right ("A photo of I" is definitely wrong!), so it's "A photo of my brother and me". "A photo of myself" is also correct, so it's "A photo of Sarah and myself."
"I went to the movies" becomes "Nathan and I went to the movies".
(An aside: always put the other person's name before yours in this situation, it's one of the very few polite grammatical forms in English! So you'd say "Nathan and I" not "I and Nathan").
"She is playing cards" becomes "Brett and she are playing cards".
"I went to Thailand" becomes "My husband and I went to Thailand".
"We are going to Scotland" becomes "Dylan and we are going to Scotland".
"They left without us" becomes "They left without Ericka and us".
"I saw the duck army marching down the road" becomes "Debbie and I saw the duck army marching down the road".
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