-ize vs -ise

Most British people regard ending words with -ize as an abomination, a symbol of creeping Americanization. They are quite wrong: even the Oxford English Dictionary endorses, even encourages, the practice in most cases, and has done for decades: 'The -ize word-ending should be used in preference to -ise where both endings are in use.'

However, -ise must be used when the verb corresponds to a noun having -is- as part of the stem, e.g. televise, and when it is identical with a noun ending in -ise, e.g. surprise. Other -ise words: advertise, advise, arise, chastise, comprise, compromise, demise, despise, devise, disguise, enterprise, excise, exercise, improvise, incise, merchandise, promise, reprise, supervise, surmise.

In verbs like analyse, catalyse, paralyse, -lys- is part of the Greek stem and not a suffix like -ize. The American spelling -yze is therefore etymologically wrong. If you care about that sort of thing.

The habit of verbizing ordinary nouns, on the other hand, actually is an abomination.