Are hyphens used correctly in the examples below? In other words, is there a rule in English that either requires or allows these hyphenations.

  • In my area of research, there is what is called the completely decomposed finite topology. Most sources write "the cdf-topology" to refer to this topology. Is this a correct hyphenation? Would it be correct to write "the cdf topology"?

  • Some source writes "the cdf-, finite and cdp-topologies", where cdp is an abbreviation for completely decomposed proper. Whereas, others write "the cdf, finite and cdp-topologies" or "the cdf, the finite and the cdp-topologies". Which one is correct, if any?

  • Some sources write "a 𝜏-cover", where 𝜏 is the Greek letter tau, used to refer to the topology the author is considering. However, all sources I have seen write "a Zariski cover", where the Zariski topology is named after the mathematician Oscar Zariski. Even when some mathematicians start with "let 𝜏 be the Zariski topology", later they write "a 𝜏-cover". Again, is the hyphen used correctly? Would it be correct to write "a 𝜏 cover"?

I have to confess that while I am asking for a rule (not only an aesthetic opinion), I do not know what constitutes a rule in English. So, I would be helpful if you could elaborate why the answer follows a rule, and not only an opinion.

  • In English, form follows usage in many things, and especially where the hyphen is concerned. Calling a prevalent usage a "rule" would be misleading. It's natural to hope for a rule that can dictate "correct" usage. There may be customs followed in specialized literature, but there aren't any reliable "rules" where hyphens are concerned. You'll find many digressions on the hyphen at ELU, such as this one. Commented Jul 16, 2017 at 18:33

2 Answers 2


A typical guideline for hyphenating nouns is

When writing out new, original, or unusual compound nouns, writers should hyphenate whenever doing so avoids confusion.

In the case of cdf-technology, we have a three-letter acronym followed by a widely understood noun. Hyphenating is unlikely to avoid confusion. In my opinion it is unnecessary, but I wouldn't go so far as to say it's wrong. An equivalent expression in everyday UK english is an HGV licence (a licence to drive a heavy goods vehicle) which is never hyphenated. Note that the german equivalent, LKW, is often hyphenated: this may have some bearing on the fact that german speakers writing in english seem to hyphenate more than native speakers.

For 𝜏-cover, we have a single letter followed by a noun. A suitable non-technical equivalent is t-shirt, which has been around for a very long time, but still there are virtually no non-hyphenated usages. Note that even when the t is replaced by tee, we still feel the need to hypenate: maybe that's because we perceive tee in this concept as a letter, not a distinct word. The same effect is observed with chi-squared: we feel the need to hyphenate because chi is not a real word but a representation of a greek letter.

For Zariski topology, there is no mistaking that Zariski is a proper name, so hyphenation is unnecessary. German speakers writing in english may, however, disagree.


I wish I could tell you that there is some rule or standard that everyone uses, but this is not the case. Nomenclature and hyphenation can vary widely, not only between various academic disciplines but also between different schools, different publications, and even different people.

If there is a standard for your area of study (I'm guessing Math) then it is likely to be an international standard, and well-documented. You'd be better off asking other mathematicians, as this is not something the average English speaker will know.

If there isn't a standard, then you're probably not the only one who is confused and annoyed, given the lack of rigor :)

  • 2
    Variations can also occur within the same field from journal to journal. Many journals have style guides that answers questions like this.
    – J.R.
    Commented Jul 16, 2017 at 21:34

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