I have mostly seen "fluxes" but I could not find a definitive answer in some dictionary. As it come from the French, I am enclined to think it is "flux" in the plural though.

Edit : I am talking about the flow of a quantity, as an air flux.

Example : "The sum of all air fluxes was zero".

  • I think "flux" is mainly used as a mass noun, like "air", thus it doesn't have a plural form.
    – Vilmar
    Feb 21, 2014 at 14:34
  • 1
    fluxes - and here I only speak of a medical problem or metallurgy. Feb 21, 2014 at 14:34
  • Context? We need to run the flux capacitors or They were in all states of flux
    – mplungjan
    Feb 21, 2014 at 14:34
  • 3
    @Vilmar Air has a plural. People put on airs all the time! I'm doing it right now in pedantically pointing this out.
    – David M
    Feb 21, 2014 at 16:42
  • 1
    @David: Yes, but you don't seem to be doing it with grace[s]. Feb 21, 2014 at 17:39

4 Answers 4


The entry for flux in the Oxford dictionaries does not show any use of flux in plural. It actually annotates some of the uses as mass nouns.

However, the plural form fluxes is often found in technical texts. Here's a quote from a very well-known text-book on Physics:

"If we now add Eqs. (3.14) and (3.15), we see that the sum of the fluxes through S1 and S2 is just the sum of two integrals which, taken together, give the flux through the original surface S=Sa+Sb." (The Feynman Lectures on Physics, Volume II)

If you still prefer to avoid the use of the plural form fluxes, you could do so by replacing the sum of fluxes with the total flux.


With @alex_reader's help, I've found that the oldest occurrence of fluxes linked by Google's n-gram viewer is:

"There are some which become tarnished by fluxes, that contain the oxydes of lead." (The circle of the mechanical arts -- Thomas Martin, 1813)

  • So the plural only stems from a technical use and did not exist before, say 1900 ? Feb 21, 2014 at 16:14
  • @alex_reader: see my last edit. 1899 is the oldest occurrance I've found. The question I'm asking myself now is whether phrases such as in all states of flux actually derive from the technical term.
    – Nico
    Feb 21, 2014 at 16:39
  • Thanks for the research. After looking at the n-gram viewer with a larger span, I think the notion may not have been much used before 1900. Even so, I think physics use mostly the notion of "flow", while mathematics may write it as a sum of several terms. Feb 21, 2014 at 16:42
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    I'd like to point out that - while Richard Feynman is one of my personal heroes - he probably shouldn't be taken as an authority on the English language; he was notoriously unconcerned about rules and correctness in anything but science.
    – MT_Head
    Feb 21, 2014 at 17:41
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    @MT_Head: Good point. I have also to say that in my experience physicists often use the expression sum of the fluxes. In fact, paraphrasing Lord Rutherford, I would say: "I have dealt with many different transformations with various periods of time, but the quickest that I have met was the transformation in one moment from a mass noun to a countable noun".
    – Nico
    Feb 21, 2014 at 17:59

I worked for a company which supplied metallurgical chemicals internationally to steel making and foundry businesses. One category of products were known as 'fluxes', each with its own product name and specification.

  • 1
    I agree. There are soldering fluxes as well. Feb 21, 2014 at 17:36

You could avoid this problem by using similar forms as one uses for "force" or "intensity". In physics on would speak of a "net force" for the sum of all forces, and the "total intensity" from various light sources, speaking of 'force' and 'intensity' as abstract qualities which are due to causes, but not belonging to those causes per se.

Thus one could say:

The net air flux was zero


The total air flux was zero.

  • 2
    This is the correct usage (especially net flux). Flux is a summation of flow, you wouldn't pluralize it.
    – David M
    Feb 21, 2014 at 16:44
  • Mathematically, a flux is simply the integral of a vector over a surface, so I do not see why there cannot be any plural. Feb 21, 2014 at 16:50
  • Whether or not a plural exists, what I've written is what is idiomatic in the North-American-Physicist dialect of English. Feb 21, 2014 at 21:29

The American Heritage Dictionary doesn't list any plural for the noun. (They have a verb flux, one of whose forms they give as fluxes.) Wiktionary gives the plural as fluxes. Your example sounds right to me:

The sum of all air fluxes was zero.

I searched the text of this book on electricity and magnetism, and found 138 uses of flux but no fluxes, but that may just mean that the need to refer to the plural doesn't come up very much.

Google ngrams shows fluxes with about 1/6 the frequency of flux, but that doesn't prove that it's correct or that it's the plural noun rather than the verbal form.

  • I think fluxes is a misappropriation of the verb form which is being incorrectly applied as a plural.
    – David M
    Feb 21, 2014 at 16:40

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