I work at an agency with a number of challenges related to nepotism and power, so I like to be super sure about my grammar critiques. The initiative I work under uses the word antiviral. However, my colleague punctuates the word with a hyphen. When is it appropriate to use anti-viral? I do not want to disclose information about the agency, so I am sorry I cannot spell out the actual name of my department, but it is something resembling Antiviral/Anti-Viral Linkage Project. We really cannot present at conferences under two different names! Also, we do not have any sort of style guide outside the authority of directors.


The Chicago Manual of Style, fifteenth edition (2003) has this guideline for hyphens in prefixes:

7.90 ... 3. Words formed with Prefixes

Compounds formed with prefixes are normally closed, whether they are nouns, verbs, adjectives, or adverbs.

A hyphen should appear, however, ... (3) to separate two i's , two a's, and other combinations of letters or syllables that might cause misreading, such as anti-intellectual, extra-alkalike, pro-life; ...

[Examples:] anti: antihypertensive, antihero, but anti-inflammatory, anti-Hitlerian

It seems clear that Chicago would favor the closed-up form antivirus. Of the style guides I checked, Chicago offers the least wiggle room to pro-hyphen dissenters.

The Associated Press Stylebook (2002) gives a general guideline and then punts to another reference work:

prefixes See separate listings for commonly used prefixes.

Generally do not hyphenate when using a prefix with a word that begins with a consonant.

Here is the AP listing for anti-:

anti- Follow the rules for prefixes and do not use a hyphen when forming a compound that does not have a special meaning and can be understood if anti is used before the base word.

Use a hyphen before proper nouns (anti-Semite) or in awkward combinations such as anti-inflation, anti-intellectual or anti-labor.

See Webster's New World Dictionary, but some exceptions that are hyphenated: anti-abortion[,] anti-bias[,] anti-labor

I don't have a copy of this dictionary, but (in view of the preferences of other recent dictionaries I checked) I would be surprised if it favored anti-virus.

Allan Siegal & William Connolly, The New York Times Manual of Style and Usage, revised edition (1999), offers what a fairly definite rule and multiple examples but ultimately turns the decision into a judgment call over whether the word would be hard to understand in closed-up from:

anti(-) Hyphenate compounds beginning with anti if they would otherwise be hard to understand (anti-abortion, anti-bias, anti-rejection, anti-vice), if the second element begins with the letter i (anti-inflation, anti-intellectual) or if the second element is capitalized (anti-American, anti-Communist, anti-Semite). An exception: Antichrist. Other anti words are solid: antiaircraft, antibiotic, antibody, anticancer, anticlimax, antifreeze, antimagnetic, antimissile, antislavery, antismoking, antisocial, antitrust, antiwar.

If you can explain why anti-bias and anti-vice need hyphens but antibiotic and antiwar don't, you have a more finely calibrated instrument of differentiation than I do. Presumably the judgment hinges on the familiarity of the word to the writer or editor—but of course reasonable minds may differ on such points.

The Oxford Guide to Style (2002) adopts a standard much like the one that the New York Times uses:

5.10.2 Prefixes and combining forms

Word with prefixes are often set as one word, but use a hyphen to avoid confusion or mispronunciation, particularly where there is a collision of vowels or consonants: [examples omitted]

The hyphen is used less in US practice. Words beginning with non- and re-, for example, are often set as one word: [examples omitted]

However, the idea that possible mispronunciation (as opposed to possible confusion) suffices to justify including the hyphen is Oxford's own. On the strength of that guideline, it seems to me, one could argue that a reader might be inclined to pronounce antivirus as though it rhymed with carnivorous—and therefore the word should be hyphenated.

For its part, The Oxford Dictionary for Writers and Editors (2000) seems unconcerned about possible pronunciation errors associated with the hyphenless forms it endorses for antilogarithm, antinovel, antiparticle, antitetanus, and antitoxin. And yet it specifies hyphens for anti-hero and anti-nuclear.

Words into Type, third edition (1974) lists anti- as being among the prefixes that "form solid words except on the occasions to be noted for homographs or when this would result in doubling a vowel." It then lists as an example of an appropriately closed-up word, antiwar.

Finally, I checked the most recent editions of various dictionaries to see how they recommend handling antiviral/anti-viral. The results:

  • Concise Oxford English Dictionary, revised tenth edition (2002): antiviral

  • The New Oxford American Dictionary (2001): antiviral

  • The American Heritage Dictionary of the English Language, fifth edition (2011): antiviral

  • Merriam-Webster's Eleventh Collegiate Dictionary (2003): antiviral

  • Webster's II New College Dictionary (1999): antiviral

  • The Random House College Dictionary, revised edition (1984): antivirus (no entry for the adjective)

So all of the modern dictionaries I consulted prefer antiviral and antivirus, but evidently some individual publishers and individual writers do not.

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  • A model well-supported, maximally definitive answer. Love the bulleted items at the end. +1 – Richard Kayser Sep 10 '16 at 2:41
  • OED3 has an entry antiviral, (updated 2003) but four of its eleven example uses are hyphenated. – Andrew Leach Sep 10 '16 at 8:44
  • @AndrewLeach: The farther back you go, the more likely "anti-" prefixes are to retain their hyphen. I don't know if that's the way the OED3 examples play out, but the tendency is for prefixes to lose their hyphens as the words become more familiar to the public (a phenomenon that some style guides seem to anticipate when they declare that hyphens are justified in situations where the closed-up form may be "confusing" or "hard to understand"). – Sven Yargs Sep 10 '16 at 8:52
  • No, hyphens occur in 1929, 1987 and 2001, and examples without in 1934, 1994 and 2001. Seems to be spread evenly throughout history, probably at something like the distribution ratio in David's answer, and probably a stylistic choice in each publication. It was just another datapoint for your survey. – Andrew Leach Sep 10 '16 at 9:09

I would advise you to employ ‘antiviral’ rather than ‘anti-viral’ on the basis of usage in the academic field of virology. Searches on the websites of two of the major journals in this field show that the usage is approx. 95% antiviral and 5% anti-viral.

Journal of Virology (US))
anti-viral : 717 (5%)
antiviral : 14,343 (95%)

Journal of General Virology (UK))
anti-viral : 26 (3%)
antiviral : 744 (96%)

The difference in totals reflects which fields are searched — the Journal of Virology search defaults to a full-text search. I tried some other journals (e.g. Virology) but the search engine on the Science Direct site they use did not distinguish between the hyphenated and unhyphenated forms of the word.

If your organization is more concerned with medical virology than basic research virology you should try journals in that area. I do not know which are the most important journals there, but obtained the following results for one, the title of which indicates that it is medical:

Journal of Medical Virology
anti-viral: 395 (15%)
antiviral: 2260 (85%)

Here there is greater usage of the hyphenated form, but the unhyphenated form still predominates.

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