Certified English teacher and language coach

Are you sometimes confused when you see ‘realize’ in one article and then ‘realise’ in another? Are you uncertain as to how to spell it? Which is correct –ise or -ize?

Good news: both of them are correct! The ending –ize is the preferred (and basically the only) spelling variation in American and Canadian English. The –ise spelling is the British English variant but –ize is also used in this language variety too. Why?

Let’s take apologise / apologize as an example:

It is a Greek loanword, it comes from the Greek verb apologize, clearly with a -z-. And that is the original spelling in British English as well: apologize.

Only later did the change from apologize to apologise take place. But it hasn’t become completely omnipresent in the British language variety, some publishers still use apologize, for example.

This is not the only example to show us that American English is the “more conservative” language variety! The Mayflower was the ship that carried the Pilgrim Fathers from England to the New World in 1620. They quite logically brought their language with them. So at that time, British and American English were obviously the same. After this period, however, these two major varieties of English drifted apart: American English retained the pronunciation and a lot of the spelling brought by the Fathers, thus remaining more conservative (but it did go on to undergo changes, like all languages do), while British English continued to develop rapidly, losing syllable-final /r/ in pronunciation, for example.

Sources: English in the United States; Grammar