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-ise and -ize

Many English verbs and some nouns can be spelt with either -ise or -ize. In American English, -ize is preferred in these cases. Examples:

  • baptise/baptize (BrE), baptize (AmE)
  • computerise/computerize (BrE), computerize (AmE)
  • mechanise/mechanize (BrE), mechanize (AmE)
  • realise/realize (BrE), realize (AmE)

Most words of two syllables, and a few longer words, have -ise in both British and American English. Examples:

  • advertise (not advertize)
  • advise
  • comprise
  • compromise
  • despise
  • devise
  • disguise
  • enterprise
  • exercise
  • franchise
  • improvise
  • revise
  • supervise
  • surprise
  • televise

Capsize has -ize in both British and American English.

Note also analyse (AmE usually analyze) and paralyse (AmE paralyze).

If in doubt, remember that in British English -ise is almost always acceptable. Some British usage guides claim that -ize is ‘preferable’ in British English on etymological and phonetic grounds, but this is not correct.

For American English, consult an American dictionary.