# Mathematicians how do you pronounce x' and x''?

**URL:** <https://boards.straightdope.com/t/mathematicians-how-do-you-pronounce-x-and-x/713137>\
**Category:** Factual Questions\
**Created:** [February 19, 2015, 10:55pm UTC](https://boards.straightdope.com/t/mathematicians-how-do-you-pronounce-x-and-x/713137 "2015-02-19T22:55:48Z")\
**Posts on this page:** 18\
**Page:** 1

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**Author:** ![griffin1977](https://avatars.discourse-cdn.com/v4/letter/g/977dab/32.png) [@griffin1977](https://boards.straightdope.com/u/griffin1977)\
**Post date:** [February 19, 2015, 10:55pm UTC](https://boards.straightdope.com/t/mathematicians-how-do-you-pronounce-x-and-x/713137/1 "2015-02-19T22:55:48Z")

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I am giving a presentation tonight, and the mathematical terms x’ and x’’ feature heavily in it. I pronounce them as “x-dash” and “x-dash-dash”, but this gets a bit tiresome by the end of the presentation.

A - Am I correct in pronouncing them this way?  
B - Is there an alternative way of saying x’ and x’’ that is less of a mouthful?

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**Author:** ![Thudlow\_Boink](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/thudlow_boink/32/320_2.png) [@Thudlow\_Boink](https://boards.straightdope.com/u/Thudlow_Boink)\
**Post date:** [February 19, 2015, 10:56pm UTC](https://boards.straightdope.com/t/mathematicians-how-do-you-pronounce-x-and-x/713137/2 "2015-02-19T22:56:48Z")

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“x prime” and “x prime prime” (or “x double-prime”)

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**Author:** ![Gary\_T](https://avatars.discourse-cdn.com/v4/letter/g/3ec8ea/32.png) [@Gary\_T](https://boards.straightdope.com/u/Gary_T)\
**Post date:** [February 19, 2015, 11:03pm UTC](https://boards.straightdope.com/t/mathematicians-how-do-you-pronounce-x-and-x/713137/3 "2015-02-19T23:03:57Z")

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X prime, X double-prime.

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**Author:** ![flight](https://avatars.discourse-cdn.com/v4/letter/f/bbce88/32.png) [@flight](https://boards.straightdope.com/u/flight)\
**Post date:** [February 19, 2015, 11:04pm UTC](https://boards.straightdope.com/t/mathematicians-how-do-you-pronounce-x-and-x/713137/4 "2015-02-19T23:04:27Z")

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I have never heard anything but “X prime”, and “X double prime”.

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**Author:** ![Thudlow\_Boink](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/thudlow_boink/32/320_2.png) [@Thudlow\_Boink](https://boards.straightdope.com/u/Thudlow_Boink)\
**Post date:** [February 19, 2015, 11:12pm UTC](https://boards.straightdope.com/t/mathematicians-how-do-you-pronounce-x-and-x/713137/5 "2015-02-19T23:12:38Z")

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[Wikipedia’s article on the prime symbol](http://en.wikipedia.org/wiki/Prime_(symbol))

Out of curiosity, what’s the context?

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**Author:** ![griffin1977](https://avatars.discourse-cdn.com/v4/letter/g/977dab/32.png) [@griffin1977](https://boards.straightdope.com/u/griffin1977)\
**Post date:** [February 19, 2015, 11:15pm UTC](https://boards.straightdope.com/t/mathematicians-how-do-you-pronounce-x-and-x/713137/6 "2015-02-19T23:15:16Z")

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I am presenting one of these…

> **[Papers We Love](https://paperswelove.org/)**
>
> A repository of computer science papers and a community of people who love reading them

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**Author:** ![Shalmanese](https://avatars.discourse-cdn.com/v4/letter/s/45deac/32.png) [@Shalmanese](https://boards.straightdope.com/u/Shalmanese)\
**Post date:** [February 19, 2015, 11:38pm UTC](https://boards.straightdope.com/t/mathematicians-how-do-you-pronounce-x-and-x/713137/7 "2015-02-19T23:38:28Z")

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X prime and X optimus prime.

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**Author:** ![John\_Mace](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/john_mace/32/185_2.png) [@John\_Mace](https://boards.straightdope.com/u/John_Mace)\
**Post date:** [February 19, 2015, 11:54pm UTC](https://boards.straightdope.com/t/mathematicians-how-do-you-pronounce-x-and-x/713137/8 "2015-02-19T23:54:48Z")

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X-prime, meaning “the first derivative of x”.

X-double-prime, meaning “the second derivative of x”.

Is this what you mean by x’ and x’’?

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**Author:** ![johnpost](https://avatars.discourse-cdn.com/v4/letter/j/f17d59/32.png) [@johnpost](https://boards.straightdope.com/u/johnpost)\
**Post date:** [February 20, 2015, 12:01am UTC](https://boards.straightdope.com/t/mathematicians-how-do-you-pronounce-x-and-x/713137/9 "2015-02-20T00:01:23Z")

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x’ is an acute accented x

x’’ is a very strongly acute accented x

or more likely

“x prime” and “x double-prime”

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**Author:** ![leahcim](https://avatars.discourse-cdn.com/v4/letter/l/b4bc9f/32.png) [@leahcim](https://boards.straightdope.com/u/leahcim)\
**Post date:** [February 20, 2015, 12:19am UTC](https://boards.straightdope.com/t/mathematicians-how-do-you-pronounce-x-and-x/713137/10 "2015-02-20T00:19:09Z")

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> [@John\_Mace](#):
>
> X-prime, meaning “the first derivative of x”.
> 
> X-double-prime, meaning “the second derivative of x”.

Sometimes primes are used just to indicate different variables of the same type. Differentiation is not _necessarily_ implied.

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**Author:** ![Jragon](https://avatars.discourse-cdn.com/v4/letter/j/e19b73/32.png) [@Jragon](https://boards.straightdope.com/u/Jragon)\
**Post date:** [February 20, 2015, 12:26am UTC](https://boards.straightdope.com/t/mathematicians-how-do-you-pronounce-x-and-x/713137/11 "2015-02-20T00:26:17Z")

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Yes, especially in computer science. You see the prime notation a lot in things like exchange arguments. “Given some edge, e, assume there is an edge e’ such that…”

You’ll see it sometimes in stuff dealing with languages with pattern matching too:

```auto

Fixpoint sum (list : natlist) : nat :=
  match list with
    | cons x list' => x + sum list'
    | nil => 0
  end.

```

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<div class="post-metadata">

**Author:** ![griffin1977](https://avatars.discourse-cdn.com/v4/letter/g/977dab/32.png) [@griffin1977](https://boards.straightdope.com/u/griffin1977)\
**Post date:** [February 20, 2015, 12:55am UTC](https://boards.straightdope.com/t/mathematicians-how-do-you-pronounce-x-and-x/713137/12 "2015-02-20T00:55:28Z")

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> [@Jragon](#):
>
> Yes, especially in computer science. You see the prime notation a lot in things like exchange arguments. “Given some edge, e, assume there is an edge e’ such that…”

This is the context I am using, e.g.: "from point x to x’ ". No derivatives are implied.

Sounds like “prime” is the correct pronunciation,.

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**Author:** ![friedo](https://avatars.discourse-cdn.com/v4/letter/f/8edcca/32.png) [@friedo](https://boards.straightdope.com/u/friedo)\
**Post date:** [February 20, 2015, 1:30am UTC](https://boards.straightdope.com/t/mathematicians-how-do-you-pronounce-x-and-x/713137/13 "2015-02-20T01:30:16Z")

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Prime is what I would say. FWIW, most people think of a hyphen (-) when one says “dash.” Or the similar printers’ em and en dashes.

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**Author:** ![Itself](https://avatars.discourse-cdn.com/v4/letter/i/d07c76/32.png) [@Itself](https://boards.straightdope.com/u/Itself)\
**Post date:** [February 20, 2015, 5:37am UTC](https://boards.straightdope.com/t/mathematicians-how-do-you-pronounce-x-and-x/713137/14 "2015-02-20T05:37:23Z")

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Joining the chorus, I’ll also say that it’s certainly “X-prime” and “X-double-prime” (or, less commonly, “X-prime-prime”). There might be some uncommon usage that’s read differently, but I can’t think of any exceptions offhand. Reading them as ‘dash’ probably wouldn’t be understood.

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**Author:** ![griffin1977](https://avatars.discourse-cdn.com/v4/letter/g/977dab/32.png) [@griffin1977](https://boards.straightdope.com/u/griffin1977)\
**Post date:** [February 20, 2015, 7:51pm UTC](https://boards.straightdope.com/t/mathematicians-how-do-you-pronounce-x-and-x/713137/15 "2015-02-20T19:51:43Z")

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I changed it to “x-prime”. But I think it may be an americanism. “x-dash” is acceptable in the in UK (the talk was in the US so changing to “x-prime” was right).

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**Author:** ![friedo](https://avatars.discourse-cdn.com/v4/letter/f/8edcca/32.png) [@friedo](https://boards.straightdope.com/u/friedo)\
**Post date:** [February 20, 2015, 8:15pm UTC](https://boards.straightdope.com/t/mathematicians-how-do-you-pronounce-x-and-x/713137/16 "2015-02-20T20:15:41Z")

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I’ve had British math and physics professors and they always said “prime.” Of course they were teaching in the US, so who knows.

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**Author:** ![bleach](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bleach/32/3106_2.png) [@bleach](https://boards.straightdope.com/u/bleach)\
**Post date:** [February 20, 2015, 8:51pm UTC](https://boards.straightdope.com/t/mathematicians-how-do-you-pronounce-x-and-x/713137/17 "2015-02-20T20:51:35Z")

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“x prime” and “x double-prime”, like everyone else has been saying. It’s usually clear from the context whether x is being differentiated (in the calculus sense of the word “differentiate”).

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**Author:** ![Machine\_Elf](https://avatars.discourse-cdn.com/v4/letter/m/82dd89/32.png) [@Machine\_Elf](https://boards.straightdope.com/u/Machine_Elf)\
**Post date:** [February 20, 2015, 9:03pm UTC](https://boards.straightdope.com/t/mathematicians-how-do-you-pronounce-x-and-x/713137/18 "2015-02-20T21:03:34Z")

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A college friend who grew up on a farm and associated priming with pumps always referred to them as “X-pumped” and “X-double-pumped.” I don’t recommend doing this in your presentation; stick with “-prime” and “double-prime.”