Leant › -ise or -ize: which does British English use?
-ise or -ize: which does British English use?
Both -ise and -ize appear in British writing. The key is to know which words never take -ize and to be consistent with the rest.
The short answer
In British English you will see organise and organize, recognise and recognize. Most British publishers, newspapers and government bodies use -ise. Oxford University Press and some academic publishers use -ize (often called Oxford spelling). In the United States, -ize is standard. So -ise is the common British choice, -ize is accepted, and mixing them in one document is the only real error.
Why both exist
Many of these verbs come from Greek, through Latin and French. The Greek ending was -izein, which became -ize in English. French used -iser, which English borrowed as -ise. Both ended up in use in Britain, while American English settled on -ize.
Words that must end in -ise
For some words -ise is not a choice, because the ending is part of the root, not a suffix. In both British and American English these are spelt -ise:
- advertise
- advise
- comprise
- compromise
- demise
- despise
- devise
- disguise
- enterprise
- exercise
- improvise
- revise
- supervise
- surprise
- televise
Do not "correct" these to -ize. A spellchecker set to US English will leave them alone, but a rushed edit might not.
Words that must end in -yse
Analyse, paralyse and catalyse are spelt with -yse in British English. American English uses -yze (analyze, paralyze). Note that -yse is not an alternative here: the -yze spelling is the American one.
Which to choose?
- Everyday UK writing: -ise (organise, realise, recognise).
- Academic or Oxford-style writing: -ize is accepted. Check the publication's style guide.
- International audiences: -ize is understood everywhere.
Check any style guide for your employer, school or publisher. If there is none, choose one and apply it throughout.
Nouns follow the verb
Organisation or organization, realisation or realization, specialisation or specialization. Match the noun to the verb you chose. The adjective forms follow too: organised or organized.
Examples in a sentence
- We will organise the event on Saturday. (UK, -ise)
- The committee will organize a vote. (accepted in the UK, standard in the US)
- The company hopes to realise a profit this year.
- Please advertise the vacancy, and revise the wording before you do. (these must stay -ise)
- The doctors will analyse the results. (UK, -yse)
If you edit other people's writing
Do not change someone's -ize to -ise (or the other way) unless you are applying a house style across the whole document. If you must pick, choose the form your organisation already uses on its website and letters, and write it down in a short style note so everyone follows it. A one-line rule such as "UK spelling, -ise endings" is enough for most teams.
Quick table
| Common UK (-ise) | Also accepted in UK / US (-ize) |
|---|---|
| organise | organize |
| realise | realize |
| recognise | recognize |
| apologise | apologize |
| criticise | criticize |
| summarise | summarize |
For other differences see the UK vs US table, and for pairs such as practice and practise go to practice or practise.