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Initially, my question was: is "focussed" or "focused" the correct past tense of "focus", but since this applies to a lot of words, I would like to generalize and ask: is there supposed to be a rule when to double the consonant?

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The OED2 says that focused and focusing are preferred, but that the “irregulars” [sic] with -ss- are often found in Britain. They give no further explanation. –  tchrist May 9 '12 at 18:11
Note that The New Yorker, that idiosyncratic stylemonger, always uses focussed and focussing. Really, it depends on what style guide a publication uses. –  Robusto Dec 30 '12 at 2:21
As you can see from the answers so far, you can spell it any way you like. Pick the one you prefer, and declare it Officially Correct, since that's in fact what everybody does. –  John Lawler Jun 2 at 0:46

4 Answers 4

up vote 6 down vote accepted

The rules are much more complicated, and I don't think it's a good idea to post them all here.

Re: doubling of the final consonant in an unstressed syllable.

Pam Peters (in "The Cambridge Guide to English Usage") argues that when the final syllable is identical with a monosyllabic word, the final consonant is also doubled in British English:

eavesdropped, kidnapped, formatted, worshipped, zigzagged etc.

Michael Swan argues that doubling in such cases is caused by a full vowel, which hasn't been reduced to a schwa.

Burchfield, the editor of the most current Fowler's, also mentions such words, as benefitted, targetted etc., without any explanation. (BrE) It's interesting that Fowler's recommends "benefitted", whereas Garner's recommends "benefited" and argues that "benefitted" is wrong ("commonly misspelled").

Final -m is usually doubled in BrE (programmed); final -l is often doubled in BrE (cancelled) etc.

The most common variant is "focused" and "focusing", both in BrE and AmE (The Longman Grammar of Spoken and Written English).

The rules are more standardized in AmE (canceled, sometimes even programed etc.)

A note on "programed": I don't use this form. It is non-existent in BrE. It's listed in all major American dictionaries as acceptable.

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I’m an American programmer (not a *programer), and I promise you I’ve never *programed anything, nor do I engage in *programing. Those simply have to be programmed and programming. Anything else is unacceptable to the point of laughability and embarrassment for the poor writer. –  tchrist May 9 '12 at 17:19
In the case of program I note that programme is an alternative (mainly British/Commonwealth) spelling. In the case of the latter there is no question whether the m should be doubled or not. Perhaps this is related to programming and programmer being the accepted variants? The single m variant does seem to occur outside of the computing context, however, so there might be a bit of an historical accident at work here (someone made a joke about Gates or Jobs being unable to spell the word correctly, though it was probably someone long before either of them.) –  Wlerin Jun 2 at 1:13

Both spellings are used depending on the variety of English. According to Wiktionary:

The spelling focused is much more common in the US; however, the spelling focussed is sometimes used in the UK and Canada, and is especially common in Australia and New Zealand.

According to the website of a UK-based company Future Perfect, the general rule is as follows:

The official requirements are that we ‘double a single consonant letter at the end of any base where the preceding vowel is spelled with a single letter and stressed’.

(Here, if the preceding vowel is the only vowel in the word, it is counted as stressed.)

However, I do not know how the spelling “focussed” fits this rule. Maybe it is an exception to the rule.

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"Focussed" probably came about because "focused" can be analysed as "fo-cused" or "foc-used", because the sequence of sounds is fairly uncommon, so the clarity of the spelling is a bit tenuous. –  Jon Purdy Nov 9 '10 at 18:03

I believe the rule is that you double the final consonant when both of the following are true:

  • the consonant ends a stressed syllable or a one-syllable word
  • the consonant is preceded by a single vowel

As 'cus' is not the stressed syllable, it would not be doubled according to this rule.

I believe the 'stressed' requirement is relaxed in some situations under British English, however. Indeed, I found references to 'focussed' with an 'especially British' tag.

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The double 's' is an aberration, an abomination and makes my eyes bleed when I read it - I posed the same question to the Oxford Word and Language Service ('OWLS') in 2009, and they replied, quoting chapter and verse (as previous contributors have), that the correct usage is single 's' but that 'some' British printing styles allow for the double 's'. Hence, it is accepted by word processing spell checkers, and people think their preference is 'right' because the spell checker lets them get away with it. Thus begin habits and opinions, uninformed by grammatical rules. Many think it is yet another difference between American English and British English, and reason that if American is single 's', British must surely be the other version - as you'll no doubt know, it is the same in both - single 's' rules!

For reference, the Guardian & Observer style guide simply states that the correct usage is single 's' (http://www.theguardian.com/styleguide/f), whilst the Economist style guide does not get around to it, stating that the word 'focus' is overused. - So stay single out there!

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What have grammatical rules got to do with spelling? –  Edwin Ashworth Dec 22 '13 at 9:49

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