King Reza: ... or, in this case, "by mistake".

Marfitalu:As far as I know, error and mistake are different in english.  A mistake is made due to lack of attention or concentration for example, but an error occures because of the person's lack of knowledge.  So an error is not avoidable while you can avoid making mistakes.  Any English speakers willing to correct me if I'm wrong?

King Reza: That's not necesarily true about error. Sometimes an error is made when you are able to do something correctly, but fail to do so. An example is a ground ball hit to the second baseball who fields it cleanly and, having plenty of time to throw the ball to the first baseman, instead throws the ball way over the first baseman's head into the stands. This is an error, and the second baseman will be charged one for his mistake. The second baseman certainly has plenty of knowledge about what to do in this instance, he didn't do it.

I hadn't thought of the two words to compare them before. They usually mean the same thing and can be used interchangeably. I'm trying to think of other times when they mean differently enough from each other that only one would be proper.

He made an error. He made a mistake.
He spoke in error. He spoke mistakenly.

Least ways it's hard for me to tell them apart. Perhaps you can give an example where only one would be proper? I can't think of an example and the words seem to have the same meaning.

While building the model airplane, he made a mistake putting the propeller together.
While building the model airplane, he made an error while putting the propeller together.

Walter Montego:I don't know for sure where only one of them can be used.  But I can give you several examples from my dictionaries so that you can see if in all cases they can be interchangeably used:

This isn't my bill.  There must be a mistake.
I made a mistake about Julie.  She's nice, really.
It was a big mistake to send her to boarding-school.
A week after the wedding she realized she had made a terrible mistake.
Make no mistakes, we're facing a major financial crisis.

The accident was the result of pilot error.
Rising costs have left us very little margin of error.

King Reza: You did find some examples! :)

This isn't my bill. There must be an error.
I made an error about Julie. She's nice, really.
It was a huge error to send her to boarding school.
A week after the wedding she realized she had made a terrible error.

>Make no mistakes, we're facing a major financial crisis.<this is a different use of mistake. Kind of idiomatic and it won't look or sound right putting error in its place.>The accident was the result of pilot mistake.<
This might be a legitimate sentence, but as you have it is the way I always heard it.

Rising costs have left us very little margin for mistakes.

Walter Montego: You can make an error in judgement, but can you make a mistake in judgement as well?

Czuch Czuckers: It seems like you can, or am I making a mistake judging it so?

:)

playBunny: Yeah, that "s" was throwing me off too. Hard to say which books and professors are teaching him English. And then there's your English as compared to my English. I bet Reza can speak as well as someone that grew up in an English speaking place, though he might have an accent. He certainly knows grammar better than most people I know.

Walter Montego:I apologize for the extra 's' that I had typed.  Looked it up now and there was no 's.'  It was 'make no mistake, .... .'

Well, about the books and professors, I use Oxford Advanced Learner's Dictionary as the main source.  What it says, I consider to be the reality and truth.  I use Websters Advanced Learner's Dictionary too, but not as frequently. 

As for my professors, I listen to what they say but never try to learn it before I check it with a more 'reliable' source such as a Native Speaker.  After all my profesors are Farsi speakers just like I. 

I am good at grammar, yes.  I use Practical English Usage, and English Grammar in Use as my main sources.  Oxford Dictionary of English Grammar and Oxford Guide to English Usage are very good and informative books that I use very often too.

And, as for whether or not I have an accent, I have always wanted to know whether a native speaker can easily understand I'm not a native or not, but I've never had the chance of speaking with a native.  maybe if one native speaker here would volunteer and listen to my recorded voice, I could understand that and let you know too! 

I especially appreciate an American and a British native speaker if possible.  

By the way, by 'And then there's your English as compared to my English.' did you mean that his English is different from yours? 

King Reza: Yes, his English is different than my English. Spoken differently, spelled differently, and even some of the grammar is done differently. Years ago someone said this of the two languages and countries. "Two countries seperated by a common language." It's kind of nonsensical, but there's some truth to it. Our cultures are different too. There's lots in common. Someday I'll travel to England to see for myself. The make some of my favorite beer there, so it's got a lot going for it from the start. :) Perhaps you can save up and travel there yourself? I think you're closer, but I'd have to check a map. I saw that it was around $750 to fly there from here the other day. I'm not sure if that was round trip or one way.

You might want to get more dictionaries. There's a tradition of them in the United States. I can't say which one is best. The American Heritage Dictionary has a lot of words in it that most of the dictionaries leave out that are common words. Perhaps some web searching would give you a few to choose from. Next to this computer I have a medium size dictionary called Webster Illustrated Contemporary Dictionary. That's my spell checker. I use it when I need to spell a word I don't know too well. Luckily I know how to spell rendezvous already because I'd never be able to find it in the dictionary without searching every "R" word in order. Just who put the "Z" and "S" in it? And why is the second letter an "E" instead of an "O"? Yeah, blame the French for English spelling. It seems like the only reason I know of. Them two countries have quite a history between them. Lots of wars and conquests. English changed a lot. More of those extra words with the same meaning playbunny alluded to. I wonder if French changed as well? How complete is that Oxford dictionary? I've never seen one of those. Does it have words in it like snafu or fubar? If so, does it say what the "f" means? And then there's this internet. I suppose that's another way to find out about languages all around the world.