“Realize” and “realise” mean the same thing. When they’re spoken out loud, they sound the same. The spelling difference is the only thing separating the two.
You may have noticed that many British books, magazines, and newspapers use the spelling “realise,” while North American publications always spell “realize” with a Z. Although the word has been around since the 17th century, there’s still no hard-and-fast rule about when to use the -ise variant, which is popular outside of the United States and Canada. BBC Americaadvises, “…The -ize ending on verbs is the most commonly acceptable version in the world. In British English, either version is fine.” In American English, only -ize is correct. If you want your writing to be accessible to American readers, we recommend using the -ize spelling.
That said, many illustrious English-language publishers in the United Kingdom and former British territories (excluding North America) still promote the -ise spelling. Although the use of realize is more common worldwide, some linguists and writers have a soft spot for the Anglicized version of the word.
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According to the Online Etymology Dictionary, the word “realize” originated with the Latin word res, meaning “property, goods, matter, thing, affair.” By Late Latin, realis meant “actual.” Next, the word made its way into the Old French language with reel and the English language with “real”, bothadjectives that mean “actual.” In French, the word réaliser, meaning “to make real,” came into usage in the 1500’s. The English started using “realize” in 1610.
As Merriam-Websternotes, the variant “realise” did not appear for another century and a half: “…First, according to the Oxford English Dictionary, in a letter by none other than lexicographer Samuel Johnson. He wrote on December 30, 1755, ‘Designs are nothing in human eyes till they are realised by execution.'” By choosing this suffix, Johnson probably intended a nod to the word’s French origins, réaliser. The –ize spelling is more consistent with Greek (-izein) and Late Latin (-izare) influences.
Noah Webster, in his influential texts on American spelling and grammar, codified the American English spelling. As his namesake dictionary explains, “In his 1806 A Compendious Dictionary of the English Language, he favored realize as well as cruize, merchandize (noun), praize, and poize.” North American writers, including Canadian English speakers, began to pick up Webster’s books and think of “realize” as the proper variant. Needless to say, “poize” and “praize” did not meet the same fate. Some –ize spellings failed to catch on with Americans, Canadians, or anyone else.
Meanwhile, the British couldn’t decide whether to favor –ise or -ize. As BBC America describes it, “Once things started to become codified, a struggle began in British English.” For words that came from Greek and Latin, the -ize ending made the most sense. For other words, especially those with longer suffixes, the -ise ending fit more comfortably. Since “realize” came from both réaliser (French) and realis (Latin), linguists could make an intelligent argument for either suffix.
Today, there’s no real consensus on the other side of the pond. BBCAmerica points out how the different spellings remain a matter of preference in the U.K., noting, “The Oxford University Press uses -ize endings in their style guide, but the Guardian does not.”
I’m an award-winning playwright with a penchant for wordplay. After earning a perfect score on the Writing SAT, I worked my way through Brown University by moonlighting as a Kaplan Test Prep tutor. I received a BA with honors in Literary Arts (Playwriting)—which gave me the opportunity to study under Pulitzer Prize-winner Paula Vogel. In my previous roles as new media producer with Rosetta Stone, director of marketing for global ventures with The Juilliard School, and vice president of digital strategy with Up & Coming Media, I helped develop the voice for international brands. From my home office in Maui, Hawaii, I currently work on freelance and ghostwriting projects.