Mathematics Stack Exchange is a question and answer site for people studying math at any level and professionals in related fields. It's 100% free, no registration required.

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

I'm not a native English speaker. A quick Google search revealed the symbol's name is apostrophe, just like in French. When used in a mathematical setting, I usually call it prime, so for instance $f'$ I'll read $f$ prime. That's the way you call it in French, but I just realized I didn't actually know whether that was the way you call it.

Thank you!

share|cite|improve this question
I am guessing it is region dependent. I am more familiar with "dash" when talking about derivative. So $f'(x)$ is f-dash x. The pronunciation could also vary with context, I suppose: when it means something other than derivative etc... – Aryabhata Jun 24 '11 at 6:03
This is part of a larger issue: Some symbols are pronounced using their name, and some are pronounced, at least in certain circumstances, using a special name. Besides the appostrophe being pronounced "prime" (when used to indicate a derivative), there are also the cases of the ampersand (&) being read "and" and the asterisk (*) being read "star". – Mike Jones Jun 25 '11 at 22:09
Strictly speaking, the prime (′) is a different character from the apostrophe ('). – Rahul Sep 2 '11 at 9:04
I would also read it as f prime. – user12205 Sep 2 '11 at 11:44
@Arjang: Not at all! If I have $f$, I can write $f(x)$, $f(y)$, $f(5)$, $f(a+b)$, and so on. Why should just $x$ go in the denominator as though it were a free variable? To be precise, $f$ is a function mapping reals to reals and has nothing to do with some $x$, unless you write $\frac{df(x)}{dx}$ as you properly should. But the prime is better, because it doesn't require you to introduce a name for the argument of $f$. Then I can write $f'(5)$ for the derivative of $f$ evaluated at $5$, instead of $\left.\frac{df(x)}{dx}\right|_{x=5}$ (yuck)! – Rahul Sep 2 '11 at 12:02
up vote 21 down vote accepted

It varies with the region.

"Prime" is how you pronounce it in American English. Here is a nice reference for American English pronounciations of math symbols; $f'$ is on the top of the second page.

"Dash" is how you pronounce it in British English: Here (search for dash).

share|cite|improve this answer
And apparently the British English one is different :-) (and concurs with what I have been using all my life!) – Aryabhata Jun 24 '11 at 6:07
In Israel we use "tag" (read like "tug"). – Yuval Filmus Jun 24 '11 at 6:08
It may have been common to pronounce $f'$ as 'f dash' in British English in 1981, but for as long as I've been learning mathematics (including eight years in a British university) I've always called it 'f prime'. – Chris Taylor Jun 24 '11 at 8:08
@Chris: I agree. "Dash" is better reserved for the en dash and em dash---those useful punctuators that you can't find on your keyboard. – John Bentin Jun 24 '11 at 8:24
At school (in England) we were taught 'f dash', 'f double dash', and so on, but at soon as I got to University (also in England) it became 'f prime'. I haven't heard anyone say 'f dash' in a long time. – Alex Jun 24 '11 at 12:14

$f'\rightarrow$ f prime

$f^{\prime\prime}\rightarrow$ f bis

$f^{\prime\prime\prime}\rightarrow$ f tris

$f^{\prime\ \backprime\prime}\rightarrow$ f tetrakis

However most people do not know these words and just say double prime, triple prime etc.

share|cite|improve this answer
Are these real names? I've done a quick google search but couldn't find any reference to any of these. – Olivier Bégassat Jan 5 '13 at 15:16
I don't like this; prime is derived from Latin, whereas the others are from Greek. – user50229 Jan 5 '13 at 15:17
@-1 Why?, do you think I made this up? – Elements in Space Jan 28 '13 at 14:13
Yes, I do (and someone else it seems). All Google references lead to Chemistry stuff. Still, by the benefit of the doubt and because it sounds funny, +1. – JMCF125 Jun 14 '13 at 16:02
I agree with f bis, being common in Swedish education. The other's I've never heard, but I haven't seem them used in notation either, f^(n) being the norm. – sapht Oct 18 '13 at 15:26

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.