Both are correct in British English. Organise and organize, realise and realize, recognise and recognize: British writers may use either ending, as long as they keep to one. American English uses -ize.
So the choice in Britain is a matter of style, not of right and wrong. -ise is the more common in British newspapers, schools and everyday writing. -ize is used by some British publishers and universities, and is known as Oxford spelling. The rest of this guide explains where each comes from, the words that never change, and the other ways British and American spelling differ.
Where the two endings come from
The ending goes back to the Greek -izein, by way of Latin -izare, which is why -ize is the older English spelling and the one Oxford spelling keeps. The -ise spelling came into English through French, which writes -iser. Both have been used in Britain for centuries.
The words that are always -ise
In some words, -ise is not an ending added to a root but part of the root itself. These are spelt -ise in British and American English alike, and -ize is wrong in either:
advertise, advise, apprise, arise, chastise, comprise, compromise, demise, despise, devise, disguise, enterprise, excise, exercise, franchise, improvise, incise, merchandise, premise, revise, supervise, surmise, surprise and televise.
A few words go the other way and are always -ize, such as capsize and size.
Analyse, paralyse and other -yse words
Words ending -yse are a separate family. British English, Oxford spelling included, writes analyse, paralyse, catalyse and breathalyse. American English writes analyze, paralyze and catalyze. So a writer using Oxford spelling writes organize but analyse.
Words made from them
Words made from the verb follow it: organise gives organisation and organised, and organize gives organization and organized. If you choose one ending, use it in all of them.
Other ways British and American spelling differ
| British | American | The pattern |
|---|---|---|
| colour, favour, honour, labour | color, favor, honor, labor | -our and -or |
| centre, theatre, fibre, litre | center, theater, fiber, liter | -re and -er |
| catalogue, analogue | catalog, analog | -ogue and -og |
| travelled, cancelled, modelling | traveled, canceled, modeling | a double l before an ending |
| fulfil, enrol, skilful | fulfill, enroll, skillful | a single l in British |
| defence, offence, pretence | defense, offense, pretense | -ence and -ense |
| licence (noun), license (verb) | license | the noun has a c in British |
| practice (noun), practise (verb) | practice | the noun has a c in British |
| anaemia, oestrogen, paediatric | anemia, estrogen, pediatric | ae and oe |
| grey, tyre, kerb, cheque | gray, tire, curb, check | words of their own |
| programme, aluminium, ageing | program, aluminum, aging | words of their own |
Two traps for British writers: a computer program is spelt program in British English too, and a metre is a length while a meter measures something, such as a gas meter.
Which should you use?
- Follow the house style if you write for a publisher, a newspaper, a school or an employer. Most have one, and it settles the question.
- For British readers in general, -ise is what most of them expect to see, and is the safer choice.
- For academic writing or a British publisher that asks for it, use Oxford spelling: -ize, but analyse.
- For American readers, use American spelling throughout, not only -ize.
- Whatever you choose, be consistent. A document that has organise on one page and organize on the next looks careless, even though both are right.
British spell check in Retroprose
Retroprose checks your spelling in British English, as you type, on every edition.
- Both endings are accepted, so organise and organize are both right, as Oxford spelling allows. The words that must be -ise, such as advise and surprise, are still marked if they end in -ize.
- American spellings are marked, such as color and center, so they never slip into a British document.
- Right-click a marked word for up to five suggestions, or run a full spell check with Ctrl+F2 or Alt+F7, which stops at each word it does not know.
- Your own words, such as the names of your characters, go in a personal word list of up to 5,000 words, kept with your account.
- A British thesaurus (Alt+F1) of about 141,000 words, with British spellings and -ise endings.
Spell check and the thesaurus run on your own device. Your text is never sent anywhere to be checked, and spell check works with no connection.
You can try the spell check now in the demo: type colour, then color, and see which one it marks.