How do you pronounce the symbol $'$ in $f'$?

Question

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!

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 06:03
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 ('). — , Sep 02 '11 at 09:04
It is not a good notation, $\frac{df}{dx}$ is far superior to this form. — jimjim, Sep 02 '11 at 11:47
@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)! — , Sep 02 '11 at 12:02
@Rahul : $f'(5)$ wins a point, however I am a devout follower of Leibniz :), but still a good point is a good point. also I like your obsorvation about not introducing extra variables, It seems intresting topic for a question — jimjim, Sep 02 '11 at 12:17
@Rahul: Heh, that reminds me: I bought this the other day and the authors insisted on keeping the prime just for denoting a "different" function, and insist on Leibniz notation everywhere else. I mean, it was sort of jarring to see what Taylor looks like in that notation (equation 0:5:1). — J. M. ain't a mathematician, Sep 06 '11 at 01:47
@Arjang: the book I was point out to Rahul might interest you. :) — J. M. ain't a mathematician, Sep 06 '11 at 01:48
As everyone is pointing names for this, in portuguese it reads "f linha" (literally, "f line") - and it is not an apostrophe nor a simple quote opening. — JMCF125, Jun 14 '13 at 16:05

score 27 · Accepted Answer · edited Jun 24 '11 at 07:16

27

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).

edited Jun 24 '11 at 07:16

Aryabhata

83,877

answered Jun 24 '11 at 06:01

Zev Chonoles

132,937

1

And apparently the British English one is different :-) http://www.uefap.com/speaking/symbols/symbols.htm (and concurs with what I have been using all my life!) – Aryabhata Jun 24 '11 at 06:07
1

In Israel we use "tag" (read like "tug"). – Yuval Filmus Jun 24 '11 at 06:08
Interesting! I hadn't heard of these variations before, I'll keep my ears open for them if I go abroad. You should post them as answers too, they are just as valid :) – Zev Chonoles Jun 24 '11 at 06:10
@Zev: I suppose it might be better if we just edit those into your answer... – Aryabhata Jun 24 '11 at 06:56
@Aryabhata: Sounds good, go ahead! – Zev Chonoles Jun 24 '11 at 07:01
@Zev: Done! I didn't do Yuval's as OP specifically asks for English and I am not sure if Isreali English is well-defined. I am also afraid, we could have an explosion of regions... – Aryabhata Jun 24 '11 at 07:16
I should have thought before, to make it community wiki. But I have done so now - thus anyone with an addition can make it. – Zev Chonoles Jun 24 '11 at 07:20
5

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 08:08
3

@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 08:24
1

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
I concur with Chris and Alex, most people in the immediate vicinity of my current office say it as 'prime', but demographically I cannot claim that most of them are in fact British. – Willie Wong Jun 24 '11 at 13:04
2

I fear the only “double dash” I've been taught in school is Mario Kart. – PseudoNeo Sep 02 '11 at 14:07

score 2 · Answer 2 · answered Jan 05 '13 at 14:14

2

$f'\rightarrow$ 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.

answered Jan 05 '13 at 14:14

Elements In Space

2,062

Are these real names? I've done a quick google search but couldn't find any reference to any of these. – Olivier Bégassat Jan 05 '13 at 15:16
I don't like this; prime is derived from Latin, whereas the others are from Greek. – user50229 Jan 05 '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
1

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

score 0 · Answer 3 · answered Feb 28 '17 at 11:10

In high school and junior-high school in Japan, we read a' as "a dash". However, in universities, it is occasionally read as "a prime" due to American influence.

I am not native speaker of English; therefore, I explored dictionaries and found a description. The Oxford English Dictionary vol. XIII (1970) states that it "usually read as `a dash' " in the explanation of the word "prime". I feel something odd in this statement, but in the explanation of the word "dash" in OED vol. III (1969), I found that "a stroke or line (usually short and straight) made with a pen or like, or resembling one, so made ....". I am now realised the symbol ' should be recognized to be a short script.

I would like rather ask why American reads a" as double prime. Why the prime (= the most important) is not only one?

The problem with dash is that it's commonly used for a hyphen (-). (Not saying that this answer is wrong, but using dash will not be widely understood.) — Glorfindel, Feb 28 '17 at 11:16
The main meaning of "dash" is "a short and rapid run". This perfectly matches the quick writing of a pen for adding ' adjacent to f, even though "prime" is an actual name of the symbol. Of course, I also use "f prime" when nobody understands "f dash". However, I don't feel "f dash" is a minority — H. Kato, Mar 01 '17 at 08:05

How do you pronounce the symbol $'$ in $f'$?

3 Answers3

Linked