In economics there are things such as "fixed" and "variable" costs. In math there are "fixed" and "variable" slopes. Is there a single word that's best to describe both of the terms at once? I've come up with measurability, gradient, and quantifiability, but I don't feel super comfortable with any of them. An example in Economics would be "The ____ of the cost is fixed."

  • My initial thoughts have to do with describing rate of change - elasticity and delta. However, I like neither term because they mean something else within economics. – TaliesinMerlin Feb 14 at 21:32
  • Value? Or does that l)+0+ – max pleaner Feb 14 at 21:41
  • @TaliesinMerlin I think those two are close. What about dynamics? I don't know if that's used in economics though. – David B Feb 14 at 22:02
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    I feel that in general, it makes the most sense to think of "fixed" as one degree of variability. So in my opinion the word you're looking for would just be "variability." (That's kind of a non-answer though.) – senderle Feb 14 at 22:41
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    This is like asking for a single word for black and white. In accounting (not economics really), there are fixed and variable costs and never the twain shall meet. They are different in essence. The type of cost is a fixed one. – Lambie Feb 14 at 22:48

You said in a comment under the question:

Variability works, and it's most likely the one I'll accept, but it is definitely odd to say "The variability of the temperature is variable".

The easiest thing to do is pick a synonym that also sounds natural—and which doesn't reuse the base words fixed or variable.

I suggest changeability. From the adjective changeable:


: capable of change: such as
a : able or apt to vary
// changeable weather
b : subject to change : ALTERABLE
// changeable plans

While still slightly odd, it suggests the following in your sentences:

The changeability of the cost is fixed.
🠆 The cost cannot be changed.

The changeability of the temperature is variable.
🠆 The temperature can change.

Note that in all cases, however, the meaning is slightly different than you intend.

If the variability of the temperature is variable, it could mean that the amount of variation can change. For instance, temperatures that used to vary between 20 degrees now vary between 40 degrees: the amount of variability has increased.

Similarly, the same could be said for the amount of changeability.

Whether it sounds odd or not, whatever word you use to come up with an abstract is going to be open to some level of ambiguity.

Therefore, it's best to simply say:

The cost is fixed.
The temperature is variable.

Or if you're thinking of a table with headings (for example), just use Fixed or Variable as the heading instead of a different word that tries to encompass both things.

  • Thank you. I think you've given the best way to look at it. – David B Feb 19 at 0:03


the type or main characteristic (of something) [Cambridge]

The nature of this cost is fixed.


You might prefer to say "The cost is fixed" or "The cost is variable"

Otherwise it seems like you want to talk about "variability".


Are you looking for "degree of stability"?

Fixed or variable cost stability.

e.g. "a degree of stability becomes a linguistic variable assuming terms such as “unstable”, “weakly stable”, “more or less stable”, “strongly stable”, “completely stable ...1

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