In science we often invent words, but that doesn't mean we know how to spell them. Most of the time words are invented by adding prefixes. In that case should there be a hyphen or not? Specifically, I need to use

  • reexcite or re-excite (reentry is similar and a official word)
  • repolarize or re-polarization

The second seems fine in the no-hyphen form, but for the first, the double "e" makes the word difficult to read. I've seen similar use with a diaeresis over the e: ë as in reëxcite, but that looks strange; any pointers?

  • 3
    The "umlaut-e" version you are talking about is called [dieresis](en.wikipedia.org/wiki/Diaeresis_(diacritic)). It is not done the way you wrote it; the e would be written twice with the dieresis placed on the second e: i.e. "reëxcite". That said, I wouldn't use it. Dieresis is quite rare in today's English except for the word naïve, where it is more common, but still totally optional. (They do use them often in The New Yorker magazine, but this is very exceptional and somewhat pretentious, in my opinion.)
    – Kosmonaut
    Dec 31, 2010 at 15:48
  • 2
    BTW, you mean hyphen, not dash. (There are two dashes in common usage, the [ en dash ](en.wikipedia.org/wiki/Dash#En_dash) and the [ em dash,](en.wikipedia.org/wiki/Dash#Em_dash) both longer than a hyphen.) Dec 31, 2010 at 15:51
  • Thanks to both @Kosmo and @Shree, I updated my question. Dec 31, 2010 at 16:20

4 Answers 4


It depends on how recent the words are. If you are concerned that your meaning will be unclear, by all means use the hyphen. Words like reentry and reelect have been in usage for a long time and pretty much no one has a problem with them. Reexcite has not, so you would do better to stick with re-excites. If you want to edit something again, you are probably better off to re-edit it if you are worried that reedit will cause the reader to stumble.

Where the prefix is not followed by a vowel, however, you are not honor-bound to add the hyphen. If you want to repolarize something, go right ahead. According to Etymonline, the word repurpose is less than 30 years old, having dropped its hyphen somewhere in the early 1980s. So if you are the first to repolarize something, you are not likely to be the last, and you will probably start a trend. In any case, your meaning will be clear.

  • 5
    In general, use a hyphen if it aids readability: this point is somewhat important when writing material that is to be consumed by people who might not be ultra-comfortable with English.
    – Suvrit
    Dec 31, 2010 at 16:22

The only thing to add to Robusto's answer is that sometimes there's no choice but to keep the hyphen, to prevent confusion. For example, recover ("get something back") vs. re-cover ("cover again").


There are two tests for deciding:

First, which way do most of your colleagues do it, reparameterized or re-parameterized?

Generally, it's standard operating procedure (SOP) to imitate your peers and colleagues because that's what they expect to see.

Second, will the version without the hyphen cause confusion or force the reader to waste time by having to look at the word a second time?

If the outcome of the second test is Yes, then use the hyphen.

There may be a third test. British English writers generally use hyphens more often than American English writers. If you're writing for a European journal or an audience of British English speakers, it might be better to use the hyphen. If the audience is primarily American, it might be better to omit the hyphen.

I don't think there should be any confusion without the hyphen, but that's just a personal opinion. Ask a couple of colleagues how they would write it.


There are words throughout English that have multiple meanings and often multiple pronunciations and these heteronyms are not in danger of being confused in context: fall, present, live, wind, wound, bass, sewer. Just because such a word starts with a prefix doesn't mean it's harder to understand. No one needs to recreate a word's common spelling or refuse a concise one nor resign to using archaic orthography. There is no reason to spell recover, recreate, resign differently to clarify the contextual meaning.

  • 1
    There’s nothing archaic about using a hyphen to separate a prefix from a root. Most of the words you mention as parallels are of different word classes, which makes it infinitely easier to tell them apart by syntactic clues alone; the ones who aren’t remain ambiguous unless context makes it clear ahead of time what you’re talking about, but there is sadly no way to distinguish them. Words like recover are equally ambiguous, sometimes even in context, but they happen to have a readily available and natural means of distinction. Advice to avoid making use of those means is just bad advice. Oct 7, 2017 at 14:28
  • As a copy editor, I am aware hyphenating prefixes is less in vogue (hence my use of "archaic"), no doubt in part to electronic communication and the simplification of spelling. (reuters.com/article/us-britain-hyphen-1/…) The dictionary spelling for email has evolved from E-mail. Advice was given to hyphenate if you fear the reader will stumble. My point: most readers can parse the syllables for a word that begins with e and has re prefixed to it without the hyphen, just as we read heteronyms without confusion. Jan 21, 2019 at 4:18

Not the answer you're looking for? Browse other questions tagged or ask your own question.