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

Many verbs that end in -ize in American English 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 English, the 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.
 
Here are the most common verbs that must end with -ise:
 
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 that always end in -yze in American English:
 
analyze
catalyze
electrolyze
paralyze
breathalyze
dialyze
hydrolyze
psychoanalyze
 
In British English, they are all spelled with the ending -yse (i.e., analyse, breathalyse, catalyse, etc.).

 

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