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I am trying to think of a word the means the rate at which a system is moving away from equilibrium.

The best example I can think of is a chemical reaction; say you have a pile of wood. If the wood is burning rapidly, this number is negative and its magnitude is large. If wood is being steadily added, the number is positive. If the number is zero, wood is being added at the same rate at which it is burning away.

** context **

The use case is a software engineering one, but abstract. Items are accumulated, and items are consumed and discarded. If items are being accumulated, you eventually run out of disk space. If items are being consumed, eventually you free up all disk space. What I am trying to convey is the speed with which the system is approaching one of those two outcomes. The outcome you're headed toward is identified by the sign of the number.

So I'm looking for a physical metaphor that I can model the terminology after.

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Are you talking about entropy? –  John Lawler May 5 at 18:09
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No, I don't think so –  Todd Freed May 5 at 18:19
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As I know, a reaction shifts the equilibrium. So, the reaction rate is how fast a reaction happens, and thus how fast the equilibrium shifts. In the end, a new equilibrium is established. Though this is related to chemical equilibrium. There can be different explanations in different systems. chemistry.stackexchange may help also. (Note: Le Chatelier's Principle is related to the topic) –  ermanen May 5 at 18:25
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Perhaps the relevant concept here is sustainable (as in "new resources are created as fast as the old ones are being used up"). –  FumbleFingers May 5 at 19:19
    
It sounds like you want something that means "net rate of change of a vector property." I'm not entirely certain, though, since that would be a term describing the degree to which a system is not in equilibrium, rather than the rate at which the system is moving away from equilibrium, and you did ask for the latter. –  user867 May 6 at 0:35

9 Answers 9

Note that a non-burning pile of wood in oxygen is NOT in equilibrium. It is in a metastable state. I think you may be thinking of "steady state," not "equilibrium."

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This does not provide an answer to the question. To critique or request clarification from an author, leave a comment below their post - you can always comment on your own posts, and once you have sufficient reputation you will be able to comment on any post. –  RyeɃreḁd May 5 at 20:45
    
Yes, burning wood is actually moving towards equilibrium with its environment at a rate that'd be measured in kilocalories per second. Of course, fire being the highly cooperative process that it is, a reaction with finite amounts of wood may never actually achieve a steady state burn rate. –  Wayfaring Stranger May 5 at 23:05

You can call that a "Chaos Vector" if you want to sound like a boss.

Entropy: The tencency of matter in the universe to move from an orderly state to a chaotic one

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A few words pop up in my head. First I thought drift, since it is simple it illustrates that one of your two options will certainly happen. You could forecast a drift rate from your current state.

I also think the word divergence would convey the same meaning and may sound better in this context although not everyone would be familiar with it.

the act of moving away in different direction from a common point

And if you wanted to get a bit scientific you could use centrifugal rate.

tending to move away from a center

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I kind of like centrifugal rate .. I may have to settle for an adverb for rate –  Todd Freed May 5 at 22:06

The closest phrases that I thought would be appropriate were "attrition rate" and "depletion rate". The rate would be positive if something is getting reduced, and negative if it's growing. Naturally, the opposite would be "growth rate".

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I believe that the word you're looking for is: Delta

Particularly in the application to system resources in a computer system many technical people are already familiar with the usage.

eg: "filesystem delta" or "memory delta" would describe the rate of change of the amount of free space available in disk or RAM respectively.

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If it was a second-order system, damping, which would be a negative number in the case of a runaway reaction.

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I'm thinking that for a single word, you might try something like decompensation, deterioration, dissipation, or devolution.

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Astatic rate or decay rate... -it depends on the type of equilibrium

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If you want a common word for an informal context, imbalance is the closest I can think of. "A widening imbalance between the supply of wood and disposal of ash ruined the furnace".

I'm sure others would be able to supply different, technical terms, used in particular circumstances. Homeostatic imbalance is used, for example, within the field of homeostasis.

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