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# Talk:Imaginary number

This article was originally a redirecty to complex number, but has been replaced by a brief explanation of the terminology and a link to that article to avoid confusion. Greg Woodhouse 10:34, 16 April 2007 (CDT)

## Confusing sentence

I don't understand the sentence

*Sometimes such complex numbers are called "pure imaginary numbers" to distinguish them from other complex numbers that are not real.*

It's not very clear what the antecedent of "such complex numbers" is; I assumed it is "a complex number whose real part is zero" and fixed the sequence accordingly. More importantly, the way I read the sentence, it says that such complex numbers are called "pure imaginary numbers" because in that way, they are are distinguished from other complex numbers. But that seems a rather odd reason; you could just as well call them simply "imaginary numbers". -- Jitse Niesen 07:59, 17 April 2007 (CDT)

- It's just a matter of mathematical practice (at least among algebraists). Numbers of the form where are called pure imaginary, and that seems completely reasonable to me, because if , then cannot be real, but it is generally not pure imaginary. At least in algebra, the distinction is a useful one, as it is in geometry. I realize I may not always express myself as well as I should, and that, as editors, you're concerned with improving the language. I also realize I've been guilty of one or two "think-o's" that look really amateurish, but that doesn't mean I don't try to choose my words carefully, as I did here. In my opinion, using informal terms like "imaginary number" in a context where they can be easily confused with pure imaginaries detracts from the article and makes it look unprofessional. But that's just my opinion. Greg Woodhouse 09:50, 17 April 2007 (CDT)

I had a look in the history. Your version is fine, but a later edit completely changed the first sentence. In the old version, "imaginary number" means any number *a* + *b*i (with *a*, *b* real) where *a* is nonzero; in the new version, *a* has to be zero. That introduced the problem I was talking about. -- Jitse Niesen 23:08, 18 April 2007 (CDT)

- I'm not sure what happened, but I believe I said that such a number is not real, but neither is it pure imaginary. Of course, it's possible that I didn't type what I was thinking. Greg Woodhouse 15:18, 20 April 2007 (CDT)

I reverted the intervening edit which changed the first sentence, so the article is now back to what you wrote. -- Jitse Niesen 21:27, 24 April 2007 (CDT)

## rewritten

I have rewritten and expanded this article, and hope that the two different uses of "imaginary" are now described clearly enough. Moreover, I have added some details on related terms. Peter Schmitt 14:30, 1 January 2010 (UTC)