# Is there a word mirroring common usage of "proportional" (which I characterize as "monotonically increasing as a function of")?

In mathematics, a and b are proportional if their ratio, a/b is constant (DEFINITION 1).

In common language, proportional is often used to mean something more like "when a goes up, b also goes up (and vice versa)" (DEFINITION 2).

I'm looking for a word other than "proportional" which matches DEFINITION 2.

• Have you already rejected the options provided by a thesaurus? thesaurus.com/browse/proportional?s=t Sep 7, 2017 at 20:54
• @filistinist - I had not, thanks. None of them seem quite right, I'm thinking I might try out "commensurably", though. Sep 7, 2017 at 20:59
• Maths language isn't so complex without good reason. Sep 7, 2017 at 22:17
• Can you add a sentence showing how you want to use the word? That will help us have a better handle on the register you want, what part(s) of speech would work for you, etc. (and it's technically required for single-word-requests). Sep 7, 2017 at 22:35

The word that springs to mind for me is correlated:

to bear reciprocal or mutual relations : correspond · If two things correlate, a change in one thing results in a similar or opposite change in the other thing.
from m-w.com

A correlation can be either positive (as A goes up, B also goes up) or negative (as A goes up, B goes down). In the absence of a qualifier, a positive correlation is generally assumed, so you should definitely specify when a correlation is negative. (You may want to specify positive correlations as well, just to be complete.)

• I don't believe that "correlation" and "proportionality" are synonyms. The former suggests there is a mutual relationship. But two things can be proportional without there being any relationship between them. There is, for example, an inverse relationship between the number of letters in the names of the month, and northern hemisphere air temperatures. Inverse proportionality exists but the two things are not correlated.
– WS2
Sep 7, 2017 at 21:17
• 'I don't believe that "correlation" and "proportionality" are synonyms.' Correct. The OP is explicitly asking for something that is not a synonym. "Correlation", or, for many scientific contexts, "Positive Correlation", seems like a perfect answer to me. Sep 7, 2017 at 21:38
• ODO (and other dictionaries) must have fallen foul of this common logical fallacy then: << correlate ... 1. verb If one thing correlates with another, there is a close similarity or connection between them, often because one thing causes the other. >> The definition of 'correlation' many mathematicians use is not the only valid one, and is probably not the principal one globally. // I'm not saying that 'correlation' isn't usable hereabouts, but there is now another different-senses problem here. Sep 7, 2017 at 21:45
• @EdwinAshworth on the contrary, your quote specifically hedges: "often because one thing causes the other". :-) Sep 7, 2017 at 21:49
• I think you'd better replace the non-standard equal sign if you want to be clear. Certainly, the two words aren't equivalent (which would perhaps be shown by the equivalence sign), but they are synonyms. The problem here is the range of senses each may have, and the question of range of synonymity. CED gives a very broad definition of correlation: << a connection or relationship between two or more facts, numbers, etc.: There's a correlation between smoking and cancer. >> This doesn't necessitate a monotonically ... Sep 7, 2017 at 22:01