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by | Oct 5, 2023

Spelling Spotlight: when to use ‘ize’ and ‘ise’

Realise or realize, organise or organize, analyse or analyze?


It might seem strange to see the same word with different spellings. Is it -ise or -ize at the end? Which one is right? You and your child might think the answer would be found in a trusted dictionary – an Oxford dictionary perhaps. But when you look, you might find that they are both correct!

There must be more to it though because some words are never spelt with an -ize ending! To find out which words can be spelt both ways, and which ones only one way, read on.

The first thing is that a dictionary will not give the ‘correct’ answer, but it will show how words are being used and spelt. If a word has two meanings, it provides both. Some words, such as foot has many more meanings: the thing at the end of your leg, a measure of length, a unit of rhythm in a poem. It also means the bottom of a hill or the muscular organ a snail uses to get about. Depending on the dictionary you are looking in, you will find all or some of these meanings. It will let you know if a word is old fashioned, for example, thrice, meaning three times. It may also tell you where a word originally came from, and this is the reason behind the different ways of spelling the same word.

It is a common belief that -ize is an Americanism and the British is -ise: recognize rather than recognise. That if you spell with a -ize, that this is an American spelling. But for most verbs, either way is correct in British English and the -ize ending has been in use in English since the 16th century. If the word came into English with its origin in the Greek root -izo, then it can be spelt -ize.

This spelling is used in a number of places including Oxford dictionaries. The National Curriculum opts for recognise and criticise although both of these words can be spelt with -ize.

Here are some words which are always spelt with -ise at the end:

  • advertise
  • advise
  • comprise
  • compromise
  • despise
  • devise
  • disguise
  • exercise
  • improvise
  • revise
  • supervise
  • surprise
  • televise


Your dictionary will tell you when a word can be spelt in different ways. It will only give one spelling for the words above. If your dictionary is an English one, rather than American, it will also only give one spelling for analyse and paralyse. These two are always spelt like this in British English.

Overall, if this still seems confusing, the most important piece of advice to give your child is to be consistent: if you start with a ‘z’ spelling, stick to it. If you are using the ‘s’ spelling, use it all the way through your writing. And, finally, remember a dictionary can tell you so much more than the meanings of tricky words.