<p>A <a href="http://www.zzgwu.com/wiki/index.php?doc-view-7730" rel="nofollow">Chinese maths site</a> has:</p>

<blockquote>
  <p>定义与定义式：<br>
  自变量x和因变量y有如下关系：<br>
  y=kx+b（k，b为常数，k≠0)</p>
</blockquote>

<p>The variable <code>k</code> is used in maths for constants — I suspect this is the intention behind using <code>k</code> for the gradient here.</p>

CC BY-SA 3.0
2012-04-22T13:04:34.780Z
2012-04-22T14:27:06.377Z
2012-04-22T14:27:06.377Z
jogloran
<p>I suspect that it originated from one of the Germanic languages, where the &quot;hard c&quot; sound in English is represented with &quot;<strong>k</strong>&quot; and thus &quot;coefficient&quot; or &quot;constant&quot; would begin with a &quot;<strong>k</strong>&quot;. I tested the hypothesis with a translator and, indeed, the terms in modern German are &quot;Koeffizient&quot; and &quot;Konstante&quot;.</p>
<p>So why would the Chinese mathematicians borrow from German/Swedish/Danish mathematicians? It might have to do with the fact that many of the leading mathematicians in the 18th-20th century were German-speaking, e.g. Euler who lived in Germany and who in fact was the first to use &quot;a,b,c&quot; to denote constants and &quot;x,y,z&quot; to denote unknowns; Leibniz, who invented much of modern calculus; Gauss, who contributed significantly to almost every field in mathematics; and other big names such as Riemann and Cantor.</p>
<p>Since the Chinese academics were just opening up to the advances in mathematics at the time, it made sense that they would borrow the notation from the leading scholars of the time.</p>
<p>What makes me more curious is why the Americans use m for slope, which don't seem to have any linguistic explanation. I did some brief reading and <a href="http://mathworld.wolfram.com/Slope.html" rel="nofollow noreferrer">this page</a> seems to have the best (non-)answer:</p>
<blockquote>
<p>&quot;J. Miller has undertaken a detailed study of the origin of the symbol <strong>m</strong> to denote slope. The consensus seems to be that it is not known why the letter <strong>m</strong> was chosen. One high school algebra textbook says the reason for <strong>m</strong> is unknown, but remarks that it is interesting that the French word for &quot;to climb&quot; is &quot;monter.&quot; However, there is no evidence to make any such connection. In fact, Descartes, who was French, did not use <strong>m</strong> (Miller). Eves (1972) suggests &quot;it just happened.&quot; &quot;</p>
</blockquote>
<p><em><strong>Edit</strong></em>: Actually, that might be wrong. I found <a href="http://www.mathsisfun.com/equation_of_line.html#Countrynote" rel="nofollow noreferrer">this page</a> which listed the common notation for slopes in many countries (based on letters from his readers). Excerpt:</p>
<blockquote>
<p>In the US, Australia, Canada, Egypt, Mexico, Portugal and Philippines the notation is:     <strong>y = mx + b</strong></p>
<p>In the UK, Germany, and former British colonies    <strong>y = mx + c</strong></p>
<p>In Azerbaijan, China, Finland, Russia and Ukraine:     <strong>y = kx + b</strong></p>
<p>In Sweden:     <strong>y = kx + m</strong></p>
<p>In Slovenia:   <strong>y = kx + n</strong></p>
</blockquote>
<p>So the Germans today in fact use &quot;m&quot; like the Americans and the British. It's certainly possible that they used &quot;k&quot; in the 19th century and shifted to the more prevalent English usage later on. But based on the data above, it seems more likely that the Chinese usage came from Russia. There could be a historical explanation for this - the Chinese Communist Party adopted Soviet science education as the basis of their curriculum after the &quot;liberation&quot;.</p>
<p>To test this <em>&quot;Soviet origin&quot;</em> hypothesis, I looked at the usage in the Nationalist-ruled province of Taiwan. And voila! The Kuomintang curriculum uses <strong>m</strong> (see <a href="http://atcm.mathandtech.org/Taiwan/Tentative_Dec10.pdf" rel="nofollow noreferrer">here</a>, page 8). This is evidence that the use of <strong>k</strong> was probably not prevalent in China before 1949.</p>
<p>So, the conclusion: The use of &quot;k&quot; was probably adopted from the Russians. There is in fact <a href="http://en.wikipedia.org/wiki/%D0%9A" rel="nofollow noreferrer">an analogue of k</a> in the Cyrillic alphabet, which looks extremely similar to the Latin k. And if you put &quot;Constant&quot; or &quot;Coefficient&quot; in a Russian translator, you'll see that they do in fact use this letter. So I stand by my theory that <em>linguistically</em> it comes from &quot;Constant&quot; or &quot;Coefficient&quot;, but I'd say the historical origin was Russian, not German.</p>

CC BY-SA 3.0
2012-04-23T09:12:31.500Z
It seems to come from Коэффициент (Coefficient), not constant. See https://encrypted.google.com/search?q=y+%3D+kx+%2B+b+%D0%9A%D0%BE%D1%8D%D1%84%D1%84%D0%B8%D1%86%D0%B8%D0%B5%D0%BD%D1%82&ie=utf-8&oe=utf-8
BertR
CC BY-SA 3.0
2012-04-23T15:41:00.553Z
Interesting answer! Just a remark. In the textbook, I was taught the French mathematician Viete(in Chinese, we call him 韦达) was the first person who introduced letters into Algebra. Wiki also supports this viewpoint. http://en.wikipedia.org/wiki/Fran%C3%A7ois_Vi%C3%A8te
Huang
CC BY-SA 3.0
2012-04-23T06:07:15.717Z
2012-04-23T06:45:56.043Z
2020-06-17T09:50:11.587Z
Yang
<p>In china they write y = kx + b</p>

<p>Just wondering if there was a reason. </p>

CC BY-SA 3.0
2012-04-22T10:52:32.167Z
I don't understand what you are referring to. Can you provide an example?
Alenanno
CC BY-SA 3.0
2012-04-22T11:07:47.980Z
its a question of why they use the variable k instead of m.  There is no proven reason why m is used in the west, just wondering if there was a reason K was used as the variable for the slope.
MaoYiyi
CC BY-SA 3.0
2012-04-22T11:17:24.210Z
My American text book uses "m". Since the Chinese borrowed their curriculum from the Europeans, it might be the same as Europe.
gonnastop
CC BY-SA 3.0
2012-04-22T11:30:01.820Z
In Europe, we usually use *y = ax+b*.
FUZxxl
CC BY-SA 3.0
2012-04-22T12:54:26.163Z
Can someone improve the question? I didn't down-vote it but it's really unclear.
Alenanno
CC BY-SA 3.0
2012-04-22T13:10:32.193Z
@Alenanno you know the formula for the equation of a line?
MaoYiyi
CC BY-SA 3.0
2012-04-22T14:35:47.410Z
On this Baidu page, they use a: http://baike.baidu.com/view/397771.htm   On this wiki page they also use a: http://zh.wikipedia.org/wiki/%E4%B8%80%E6%AC%A1%E6%96%B9%E7%A8%8B#.E5.BE.AE.E5.88.86 and on this one they use m http://zh.wikipedia.org/wiki/%E6%96%9C%E7%8E%87
BertR
CC BY-SA 3.0
2012-04-23T06:26:40.980Z
BertR: I checked the history of those Wikipedia pages and they were written by someone from Hong Kong, which uses the British system.
Yang
CC BY-SA 3.0
2012-04-23T07:06:03.053Z
As for the Baidu page, you linked to the page on "Linear equation in one unknown" whereas y=kx+b is a linear equation in two unknowns. Based on my experience, the use of a,b,c, as coefficients in equations where all the unknowns are on one side is the worldwide standard. It's only when we need to emphasize the "slope" of a line (the linear relationship between two unknowns) that we use m or k.
Yang
<meaning>
Why in China do they use k instead of m for the slope of a line?
# Why in China do they use k instead of m for the slope of a line?

(Asked by: username_0 on 2012-04-22)

In china they write y = kx + b

Just wondering if there was a reason.

**Tags:** meaning

> **Comments:**
> **username_1**: I don't understand what you are referring to. Can you provide an example?  
> **username_0**: its a question of why they use the variable k instead of m.  There is no proven reason why m is used in the west, just wondering if there was a reason K was used as the variable for the slope.  
> **username_2**: My American text book uses "m". Since the Chinese borrowed their curriculum from the Europeans, it might be the same as Europe.  
> **username_3**: In Europe, we usually use *y = ax+b*.  
> **username_1**: Can someone improve the question? I didn't down-vote it but it's really unclear.  
> **username_0**: @username_1 you know the formula for the equation of a line?  
> **username_4**: On this Baidu page, they use a: http://baike.baidu.com/view/397771.htm   On this wiki page they also use a: http://zh.wikipedia.org/wiki/%E4%B8%80%E6%AC%A1%E6%96%B9%E7%A8%8B#.E5.BE.AE.E5.88.86 and on this one they use m http://zh.wikipedia.org/wiki/%E6%96%9C%E7%8E%87  
> **username_5**: username_4: I checked the history of those Wikipedia pages and they were written by someone from Hong Kong, which uses the British system.  
> **username_5**: As for the Baidu page, you linked to the page on "Linear equation in one unknown" whereas y=kx+b is a linear equation in two unknowns. Based on my experience, the use of a,b,c, as coefficients in equations where all the unknowns are on one side is the worldwide standard. It's only when we need to emphasize the "slope" of a line (the linear relationship between two unknowns) that we use m or k.  

---

## 2 answers

### Answer by username_5 on 2012-04-23. Score: 5 | Accepted answer

I suspect that it originated from one of the Germanic languages, where the "hard c" sound in English is represented with "**k**" and thus "coefficient" or "constant" would begin with a "**k**". I tested the hypothesis with a translator and, indeed, the terms in modern German are "Koeffizient" and "Konstante".

So why would the Chinese mathematicians borrow from German/Swedish/Danish mathematicians? It might have to do with the fact that many of the leading mathematicians in the 18th-20th century were German-speaking, e.g. Euler who lived in Germany and who in fact was the first to use "a,b,c" to denote constants and "x,y,z" to denote unknowns; Leibniz, who invented much of modern calculus; Gauss, who contributed significantly to almost every field in mathematics; and other big names such as Riemann and Cantor.

Since the Chinese academics were just opening up to the advances in mathematics at the time, it made sense that they would borrow the notation from the leading scholars of the time.

What makes me more curious is why the Americans use m for slope, which don't seem to have any linguistic explanation. I did some brief reading and [this page](http://mathworld.wolfram.com/Slope.html) seems to have the best (non-)answer:

> "J. Miller has undertaken a detailed study of the origin of the symbol **m** to denote slope. The consensus seems to be that it is not known why the letter **m** was chosen. One high school algebra textbook says the reason for **m** is unknown, but remarks that it is interesting that the French word for "to climb" is "monter." However, there is no evidence to make any such connection. In fact, Descartes, who was French, did not use **m** (Miller). Eves (1972) suggests "it just happened." "

***Edit***: Actually, that might be wrong. I found [this page](http://www.mathsisfun.com/equation_of_line.html#Countrynote) which listed the common notation for slopes in many countries (based on letters from his readers). Excerpt:

> In the US, Australia, Canada, Egypt, Mexico, Portugal and Philippines the notation is: **y = mx + b**
>
> In the UK, Germany, and former British colonies **y = mx + c**
>
> In Azerbaijan, China, Finland, Russia and Ukraine: **y = kx + b**
>
> In Sweden: **y = kx + m**
>
> In Slovenia: **y = kx + n**

So the Germans today in fact use "m" like the Americans and the British. It's certainly possible that they used "k" in the 19th century and shifted to the more prevalent English usage later on. But based on the data above, it seems more likely that the Chinese usage came from Russia. There could be a historical explanation for this - the Chinese Communist Party adopted Soviet science education as the basis of their curriculum after the "liberation".

To test this *"Soviet origin"* hypothesis, I looked at the usage in the Nationalist-ruled province of Taiwan. And voila! The Kuomintang curriculum uses **m** (see [here](http://atcm.mathandtech.org/Taiwan/Tentative_Dec10.pdf), page 8). This is evidence that the use of **k** was probably not prevalent in China before 1949.

So, the conclusion: The use of "k" was probably adopted from the Russians. There is in fact [an analogue of k](http://en.wikipedia.org/wiki/%D0%9A) in the Cyrillic alphabet, which looks extremely similar to the Latin k. And if you put "Constant" or "Coefficient" in a Russian translator, you'll see that they do in fact use this letter. So I stand by my theory that *linguistically* it comes from "Constant" or "Coefficient", but I'd say the historical origin was Russian, not German.

> **Comments:**
> **username_4**: It seems to come from Коэффициент (Coefficient), not constant. See https://encrypted.google.com/search?q=y+%3D+kx+%2B+b+%D0%9A%D0%BE%D1%8D%D1%84%D1%84%D0%B8%D1%86%D0%B8%D0%B5%D0%BD%D1%82&ie=utf-8&oe=utf-8  
> **username_7**: Interesting answer! Just a remark. In the textbook, I was taught the French mathematician Viete(in Chinese, we call him 韦达) was the first person who introduced letters into Algebra. Wiki also supports this viewpoint. http://en.wikipedia.org/wiki/Fran%C3%A7ois_Vi%C3%A8te  

---

### Answer by username_6 on 2012-04-22. Score: 1

A [Chinese maths site](http://www.zzgwu.com/wiki/index.php?doc-view-7730) has:

> 定义与定义式：  
> 自变量x和因变量y有如下关系：  
> y=kx+b（k，b为常数，k≠0)

The variable `k` is used in maths for constants — I suspect this is the intention behind using `k` for the gradient here.


---

