In my academic work (physics), I often use a noun as an adjective, and this seems to be a common practise to avoid long sentences. For instance sphere packing stands for packing made of spheres.

  1. Is that correct? Is there a reason to avoid doing that?
  2. What if I am given information about the spheres: they are soft spheres? I should talk about a soft-sphere packing, right?
  3. Is the hyphen between soft and sphere mandatory, optional, or wrong? Is that always the case when an adjective-noun group becomes an adjective? References are appreciated!

Here are a few examples taken from my work. Some come from a plural, others from a singular. Please correct them if they are wrong.

  • Soft-sphere packings (packings made of soft spheres)
  • Infinite-dimensional limit (limit in which the dimension tends to infinity)
  • Low-connectivity particles (particles having a low connectivity)
  • Sparse-matrix methods (methods used with sparse matrices)
  • Non-zero energy (energy not being zero)
  • Non-zero-energy mode (mode having an energy that is not zero)
  • Thanks! Being French, I had a problem with the hyphen/dash distinction (both are tirets in French). If I got it right: hyphen = trait d'union = tiret court / dash = tiret long.
    – styko
    Commented Aug 10, 2015 at 2:21
  • @styko: that sounds right to me. Though there are two types of dashes in some styles of English typography-- em dashes and en dashes. The em dash is quite long, sometimes used with spaces around it, and usually applies to entire phrases or clauses. The en dash is intermediate between the hyphen and em dash in length, and in a way in usage: it's used to link juxtaposed words, as in ranges, oppositions and apparently in some cases compound adjectives! (I suppose this means your examples might be en dashes after all for some typesetters.) thepunctuationguide.com/en-dash.html
    – herisson
    Commented Aug 10, 2015 at 2:27
  • 2
    None of these hyphens are wrong. I think the only ones that are mandatory are non-zero energy (because non is not a word by itself) and maybe soft-sphere packing (because without the hyphen people might interpret it as a sphere packing that was soft). That is, you should consider the hyphens optional if there's no ambiguity. Commented Aug 10, 2015 at 2:38
  • 1
    It is quite normal to use nouns attributively in English to modify other nouns (what you are calling “used as an adjective”). And yes, it does make for shorter sentences than if you used a prepositional phrase connected with de as in French. It can also lead to confusion if you stack them up too long, which is why people sometimes use hyphens to connect pieces of them to resolve potential ambiguity as Peter mentions. It’s so they know which part applies to what: a stolen-cheese sandwich versus a stolen cheese-sandwhich, perhaps as an example where it might matter..
    – tchrist
    Commented Aug 10, 2015 at 3:00

1 Answer 1


The sample phrases you included look good to me except the last one: my guess is non-zero energy mode is more common.

Others have given you the things to think about when deciding whether to use a hyphen or not. Keep in mind, though, that in your field, certain combinations of words become commonplace, and the hyphen sometimes gets dropped. There are two things you can do to have more confidence about your manuscripts --

  • search for the phrase in google scholar, to see whether other people are hyphenating. Limit your search to the last few years, though, since these things change over time.

  • ask a native speaker of English in your field to read through your manuscript.

Lastly I would like to reassure you that your readers will be focusing on your results and your analysis, not your hyphens -- so it won't be a biggie if you have a weird hyphen here or there.

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