The -ize have it

Most translators and editors work on the basis that the -ise suffix is British and -ize is American. So we have realise/realize, advertise/advertize, analyse/analyze, as well as the derived forms realisation/realization and so on.

As usual, the reality is more complex. Here are some things which upset the simple rule:

1. There is no rule that British spelling must use -ise in words like “realise”. Pick up any book published by Penguin, for example, and you’ll find they standardise on -ize. The OED (Oxford English Dictionary) prefers and recommends -ize, with -ise as an optional alternative, but in practice a majority of Brits (and Australians) use -ise.
2. Just as Brits tend to assume -ise is always correct, Americans tend to assume -ize is the only form for them. In fact, the following have -ise in all cases, in both Britain and America (check with www.merriam-webster.com if you don’t believe me):
   

   advertise advise affranchise apprise (inform) arise braise chastise circumcise comprise compromise concise demise despise devise

   disfranchise disguise emprise enfranchise enterprise excise exercise expertise franchise guise improvise incise merchandise misadvise

   misprise mortise practise precise premise prise (open) reprise revise seise (legal term) supervise surmise surprise televise treatise

3. (from Judith Butcher, Copy Editing for Editors, Authors and Publishers: The Cambridge Handbook, Third Edition, 1992, p. 160)
4. There are a few words where -ize is obligatory too, such as capsize, size, seize and prize (when it means “appraise”).
5. Curiously, this means that if you use -ize for the cases which are optional in Britain and -ise for the obligatory ones in both countries, you end up with spelling which is acceptable on both sides of the Atlantic.
6. We tend to assume that British spellings are older than American, and that it was Noah Webster who instigated changes such as colour/color, draught/draft. But in this case it’s the -ize forms which are traditional, (via Greek and Latin) and it was Britain which changed over to the more French-looking -ise forms in the last couple of centuries.