Verbs ending in -ize, -ise, -yze, and -yse

Many verbs that end in -ize can also end in -ise in British English. For example, in British English, all of the following spellings are acceptable: finalize/finalise; organize/organise; realize/realise. In American Englishthe only correct spellings are finalize, organize, and realize.  

In both American and British English, there is a small set of verbs that must always be spelled with -ise at the end. 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') in promise.

advertise compromise exercise revise
advise despise improvise supervise
apprise devise incise surmise
chastise disguise prise (meaning ‘open’) surprise
comprise excise promise televise


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

analyse catalyse electrolyse paralyse
breathalyse dialyse hydrolyse psychoanalyse


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

analyze catalyze electrolyze paralyze
breathalyze dialyze hydrolyze psychoanalyze

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

See more from Endings beginning with vowels