British vs. American English: -Ise or -Ize?

The verb endings “-ise” and “-ize” often get confused. Usually, the correct ending depends on which English dialect your client is using. Here’s our guide on using these spellings in British and American English and what you need to consider when proofreading. 

British vs. American Spelling

For the most part, American English uses the spelling “-ize” exclusively:

She didn’t realize spelling could be so complicated.

He wants to organize the books by color.

I specialize in grooming guinea pigs.

If you’re proofreading a document written in American English and your client uses the “-ise” suffix, this will need to be corrected.

British English, on the other hand, usually favors the “-ise” spelling. However, it’s still technically correct to use the spelling “-ize” when writing in British English, as long as this spelling is used consistently:

She didn’t realise/realize spelling could be so complicated.

He wants to organise/organize the books by colour.

I specialise/specialize in grooming guinea pigs.

As with most aspects of the English language, though, the rule has exceptions.

Exceptions to the Dialect Rule

Some words are always spelled with one suffix, regardless of which dialect is being used. This can be because the actual suffix is a compound or part of a longer word or because the word itself is not a verb. Some examples include:

• “Despise” from the Latin words de (“down”) and specere (“look at”).
• “Compromise” from the Latin words com (“together”) and promissus (“promise”).
• “Advertise” from the noun “advertisement.”
• “Capsize” from the Spanish word capuzar (“to sink headfirst”).
• “Prize,” a noun referring to a reward in a competition (not to be confused with the verb “to prize/prise open”)

You will need to keep an eye out for these and similar words in your client’s writing and be careful not to alter them. Changing “compromise” to “compromize,” for example, would be incorrect, even in American English.

Tips for Proofreading Word Endings

Now that you know the rules for spelling “-ise” and “-ize” words, here are some tips on how to find and deal with them when proofreading.

1. Set the Proofing Language

When you open a document to start editing, one of the first things you should do is set the proofing language to either British or American English. 

In Microsoft Word, you can do this by going to the Review tab and selecting Language > Language Preferences > Office authoring languages and proofing or Language > Set Proofing Language.

In Google Docs, go to File > Language and select your preferred dialect.

This should highlight most of the “-ise”/“-ize” spelling errors in the document. However, be aware that you shouldn’t just rely on this tool, especially if your client is using a style guide that advocates non-standard spelling.

2. Check the Style Guide

Occasionally, your client may be following a style guide that advocates for an alternative spelling than the one expected for the dialect. If this is the case, you should prioritize the spelling recommended by the style guide.

It also means that you should pay special attention to your client’s “-ise” and “-ize” spellings in case they have missed this requirement.

3. Look Out for Inconsistencies

While British English usually accepts both the “-ise” and “-ize” spelling, your client will need to be consistent with the spelling they choose. If, for example, they have spelled the word “realize” as both “realise” and “realize” in the same document, you’ll need to correct these to either:

• The spelling that occurs most often
• The “-ise” version of the word to keep with standard British English spelling

4. Use the Search Function

You can use the search functions in your word processor to locate “-ise” and “-ize” words.

In Word, go to Home > Find and type in either “is” or “iz” to find the suffix you’re looking for. This will help you to locate words that don’t end in “e” but could still be affected by the misuse of the suffix, such as “realising/realizing”.

You can use the same tool in Google docs.

Remember, not every word ending in “-ise” or “-ize” will need to be corrected to the alternative spelling. 

When you use search tools, check each instance containing the suffix separately so that you only change the spellings that are actually incorrect.

5. Leave Your Client a Comment

If you come across multiple misuses of the “-ise” or “-ize” spelling, consider leaving a comment for your client explaining the issue. You should also do this if you have replaced all instances of one spelling with the other to check that this is the author’s preference.

Becoming A Proofreader

Our Becoming A Proofreader course will teach you all you need to know about proofreading different dialects (and lots more!). If you think proofreading could be the career for you, sign up for a free trial and start your freelance journey.

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