# Math Term, Kinda "Proportional" **URL:** \ **Category:** Factual Questions\ **Created:** [January 20, 2006, 7:45pm UTC](https://boards.straightdope.com/t/math-term-kinda-proportional/340872 "2006-01-20T19:45:48Z")\ **Posts on this page:** 11\ **Page:** 1
**Author:** ![Jon\_the\_Geek](https://avatars.discourse-cdn.com/v4/letter/j/bbce88/32.png) [@Jon\_the\_Geek](https://boards.straightdope.com/u/Jon_the_Geek)\ **Post date:** [January 20, 2006, 7:45pm UTC](https://boards.straightdope.com/t/math-term-kinda-proportional/340872/1 "2006-01-20T19:45:48Z")
If I say “y is proportional to x,” I mean y = kx. If I say “y is proportional to the square of x,” I mean y = kx^2. If I say “y is proportional to the cube of x,” I mean y = kx^3. Is there a general term for “y = kx, or y = kx^2, or y=kx^3, etc”. In other words, as y increases, x increases, but you don’t know exactly what the relationship is? ---
**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:** [January 20, 2006, 7:52pm UTC](https://boards.straightdope.com/t/math-term-kinda-proportional/340872/2 "2006-01-20T19:52:00Z")
y increases monotonically as a function of x. ---
**Author:** ![jawdirk](https://avatars.discourse-cdn.com/v4/letter/j/df705f/32.png) [@jawdirk](https://boards.straightdope.com/u/jawdirk)\ **Post date:** [January 20, 2006, 8:12pm UTC](https://boards.straightdope.com/t/math-term-kinda-proportional/340872/3 "2006-01-20T20:12:46Z")
y correlates positively with x ---
**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:** [January 20, 2006, 8:19pm UTC](https://boards.straightdope.com/t/math-term-kinda-proportional/340872/4 "2006-01-20T20:19:09Z")
This may be a nitpick, but if y = kx[sup]2[/sup], you can’t say y increases whenever x increases if there’s a possibility that x could be negative. ---
**Author:** ![ultrafilter](https://avatars.discourse-cdn.com/v4/letter/u/3d9bf3/32.png) [@ultrafilter](https://boards.straightdope.com/u/ultrafilter)\ **Post date:** [January 20, 2006, 8:35pm UTC](https://boards.straightdope.com/t/math-term-kinda-proportional/340872/5 "2006-01-20T20:35:35Z")
It’s probably a weaker condition than what you’re looking for, but you can say that y [symbol]Î W/symbol. What this means is that there are constants n and c such that, whenever x \> n, y \> cx. ---
**Author:** ![Happy\_Fun\_Ball](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/happy_fun_ball/32/17664_2.png) [@Happy\_Fun\_Ball](https://boards.straightdope.com/u/Happy_Fun_Ball)\ **Post date:** [January 20, 2006, 8:57pm UTC](https://boards.straightdope.com/t/math-term-kinda-proportional/340872/6 "2006-01-20T20:57:13Z")
How about y is proportional to a polynomial in x… (k, kx, kx^2,… are all polynomials in x as are any linear superposition) ---
**Author:** ![TJdude825](https://avatars.discourse-cdn.com/v4/letter/t/dec6dc/32.png) [@TJdude825](https://boards.straightdope.com/u/TJdude825)\ **Post date:** [January 21, 2006, 12:58am UTC](https://boards.straightdope.com/t/math-term-kinda-proportional/340872/7 "2006-01-21T00:58:18Z")
> [@Eyer8](#): > > How about y is proportional to a polynomial in x… (k, kx, kx^2,… are all polynomials in x as are any linear superposition) I think “monomial” or even “monomial with positive coefficient” might be better, because -x^2+12x-5 is a polynomial, but doesn’t seem to fit here. ---
**Author:** ![David\_Simmons](https://avatars.discourse-cdn.com/v4/letter/d/9de053/32.png) [@David\_Simmons](https://boards.straightdope.com/u/David_Simmons)\ **Post date:** [January 21, 2006, 3:07am UTC](https://boards.straightdope.com/t/math-term-kinda-proportional/340872/8 "2006-01-21T03:07:30Z")
Here are[plots of the equations](http://pg.photos.yahoo.com/ph/dwsimm2000/detail?.dir=8cf7&.dnm=2289scd.jpg&.src=ph) with k = 3 and x running from -2 to 2 in steps of 0.1. Is there anything that describes all three other than that they are functions of x? ---
**Author:** ![Jon\_the\_Geek](https://avatars.discourse-cdn.com/v4/letter/j/bbce88/32.png) [@Jon\_the\_Geek](https://boards.straightdope.com/u/Jon_the_Geek)\ **Post date:** [January 21, 2006, 2:23pm UTC](https://boards.straightdope.com/t/math-term-kinda-proportional/340872/9 "2006-01-21T14:23:58Z")
> [@jawdirk](#): > > y correlates positively with x Everyone had great answers to the question as I actually asked it, but this is what I was looking for (the cases in which I want to use it fit the conditions necessary to make this true, and I’m looking for something that the reader could grok without having to learn any new words, only a new way to put those words together). Thanks! ---
**Author:** ![ultrafilter](https://avatars.discourse-cdn.com/v4/letter/u/3d9bf3/32.png) [@ultrafilter](https://boards.straightdope.com/u/ultrafilter)\ **Post date:** [January 21, 2006, 5:08pm UTC](https://boards.straightdope.com/t/math-term-kinda-proportional/340872/10 "2006-01-21T17:08:02Z")
Saying that y correlates positively with x allows for many more relationships than the ones you mention (y = k\*log(x), y = k[sup]x[/sup], etc.), so be careful how you use it. ---
**Author:** ![Jon\_the\_Geek](https://avatars.discourse-cdn.com/v4/letter/j/bbce88/32.png) [@Jon\_the\_Geek](https://boards.straightdope.com/u/Jon_the_Geek)\ **Post date:** [January 22, 2006, 1:27am UTC](https://boards.straightdope.com/t/math-term-kinda-proportional/340872/11 "2006-01-22T01:27:00Z")
> [@ultrafilter](#): > > Saying that y correlates positively with x allows for many more relationships than the ones you mention (y = k\*log(x), y = k[sup]x[/sup], etc.), so be careful how you use it. Yeah. It’s what I meant to ask for. For example, if someone has two data points, something like (1,2) and (2,4), they can say y seems to correlate positively with x, but they can’t really say anything more until they gather more data (and, of course, they can’t even say that with any certainty). That’s all I needed 🙂