-ize, -ise, or -yse?

Many verbs that end in -ize can also end in -ise: both endings are correct in British English, though you should stick to one or the other within a piece of writing. For example: finalize/finalise; organize/organise; realize/realise. This website spells these words with the -ize ending, but the main dictionary entries for the verbs show that the -ise spelling is also correct.

But there is a small set of verbs that must always be spelled with -ise at the end and never with -ize. The main reason for this is that, in these words, -ise is part of a longer word element rather than being a separate ending in its own right. For example: -cise (meaning ‘cutting’) in the word excise; -prise (meaning ‘taking’) as in surprise; or –mise (meaning ‘sending’) as in promise. Here are the most common ones:

chastisedisguiseprise (meaning ‘open’)surprise


There are also a few verbs which always end in -yse in British English.



In American English, they are all spelled with the ending -yze

You can read more about the use of ‘ize’ and ‘ise’ on the Oxford Dictionaries blog. Here you will find more information about the historical usage of ‘ize’ and ‘ise’ and the difference between the two in the context of British English and American English.


Back to spelling.

You may also be interested in

Words containing the letter q

Spelling rules and tips

Common misspellings

Grammar and usage