As always, it's down to simple rules that, to get right, all you need to do is learn them and practise them (much like tying your shoelaces, riding a bike, or feeding yourself without getting custard in your eye). Here they are:
If you say "I bought a loaf of bread," you're telling someone that you purchased it. Money changed hands, and the loaf of bread now belongs to you to do with as you will, whether that's make toast, have a sandwich, feed the ducks or give it to someone as a gift.
That simple little 'r', inserted between the 'b' and the 'o' changes the meaning of the word completely, yet people so often say 'brought' when actually the word they were looking for was 'bought'. I don't so regularly see the mistake made the other way around, though, which is odd: most travesties of spelling, grammar and punctuation stem from people trying to give their poor little fingers a rest from typing so many nasty, effort-inducing characters.
If you say "I brought a loaf of bread," you're telling someone that you moved a loaf of bread from somewhere to somewhere else. The idea that you purchased it from a supermarket, a bakery or a bloke called Kevin in an alley doesn't get a mention.
The difference is subtle, and the two meanings can overlap quite a lot. For example, it's quite likely that if you bought a loaf of bread you also brought it home. To get it right, you need to think about what you mean:
- "I have brought you a present!" - I have been kind enough to find something that I thought you'd like as a gift, and bring it to you.
- "I have bought you a present!" - I parted with some hard-earned cash in order to buy you something that I thought you'd like.
The Bottom Line
- Use bought when you're talking about how you paid for something.
- Use brought when you're talking about how you moved something.
* Actually, the truth of the matter is that every time I hear or see someone get this wrong, the Augmented Reality part of my brain supplies a brief but noticeable overlay of fiery burningness across my entire field of vision. Yes, it's disturbing, and yes, I should get it looked at.