Defense vs. Defence in Canadian English

I'm Canadian and work with Canadian editors.

The Canadian Oxford Dictionary (2nd ed.) often provides both British and American spellings of words. Sometimes the British spelling comes first, and other times it's the American spelling that comes first. (It's not actually true that we always prefer one over the other.)

In all cases, the one that's listed first is more common that the other—but both are "correct."

It's the house style of any particular publisher that determines what's used for their publications. Many Canadian publishers and companies decide that if a word has both British and American variations, it's the first variation that should be used. But it's not a universal decision—and it's only a matter of style, not of a single dictionary entry.

Defence is not the sole official spelling of the word in Canada—defense is also an official spelling in Canada.

However, it's the style choice of Canadian government publications to only use defence—which is something quite different.

From the Canadian Oxford Dictionary (2nd ed.):

de·fence/dɘ'fens/noun (also de·fense)

de·fence·man (noun) (pl -men) (esp. US de·fense·man)

Software that uses Canadian English dictionary rules should (and commonly does) mark both spellings as correct.

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I suspect that the use of defense in the National Post was an unintentional typo. While still in the dictionary, it's likely that it goes against their house style and simply went unnoticed.

I should add that many people, in less formal settings, frequently do use the secondary spelling of many of these words as a matter of personal choice.

I know one Canadian editor who insists on the British c for nouns and insists s be used for verb forms. He’s silly, but he’s the boss. Either is fine with me, neither will confuse anyone. But consistency in any one work is advisable. As to ‘official’ spelling. There is no such thing in Canada! We have no academy to govern language, unlike France with French. And the French authority is widely ridiculed and ignored. Le hotdog still rules!

Canadian newspapers, however, do have an official style guide: The Canadian Press Stylebook, supplemented by The Canadian Press Caps and Spelling. It says "defence (not defense), but defensive."

The editor insisting on c for nouns and s for verb forms is following CP style: "practice (n. or adj.), practise (v.)"