'ise' vs 'ize'

Posted by James Briggs on March 14, 2002

The following comes from 'Mind the Gaff. The Penguin Guide to Common Errors in English'. by (Prof) RL Trask. Pengiun Books 2001. By the way, he's an American working at the University of Sussex in England.

I was given the book for Christmas and thought this section particularly worth reproducing.
-ize, -ise
There are two groups of words here, and these should not be confused.

The first group consists of words which are always spelled with -ise in all varieties of English. The most frequent verbs in this group are advertise, advise, apprise, chastise, circumcise, comprise, compromise, despise, devise, disguise, excise, exercise, improvise, supervise, surmise, surprise and televise, to which we may add the nouns demise, enterprise, franchise and merchandise, some of which are occasionally used as verbs. These words do not contain the Greek suffix -ize and may never be spelled with -ize. British writers attempting to use American spelling sometimes slip up here and write, for example, *advertize, which is never acceptable.

The second, and much larger, group consists of verbs containing the Greek suffix -ize. Among these are realize, civilize, ostracize, jeopardize, organize and trivialize; there are far too many to list here, and new ones are coined almost at will, like hospitalize, finalize and prioritize. These words must be spelled with -ize in American English. In British English, the spelling with -ize is traditional, and is still preferred in many conservative quarters, for example at the Oxford University Press. But the newer spelling in -ise is now widespread in Britain and is preferred in other quarters. British writers may use whichever spelling they prefer, unless they are writing for a publishing house which insists upon one or the other.

Whichever spelling you prefer, you must, of course, be consistent, and use it exclusively, not only with the verbs but with their derived nouns like realization and civilization.

There is a complication with the verb exorcize, exorcise. Historically, this word contains the suffix -ize, and so it should be spelled exorcize in the style that uses -ize. However, many people no longer perceive this as containing the suffix, and so it is sometimes spelled exorcise even in the style with -ize.

Note also the unusual word capsize, which is spelled -ize in all varieties.