Although there exists an ocean of differences between British and American English, there aren’t many documented or strict rules on whether or not it’s acceptable to mix the two.
The reason for this could be traced to the fact that drawing distinctions between the two can be a little confusing. It is not uncommon that a non-American national, who grew up in North America, would have an American accent, but some or most of his or her vocabulary would be derived from British English (or even Australian or Canadian English).
While a Brit would say, “I take French class from Monday to Thursday”, your American friend would say, “I take French class Monday through Thursday.” For a mix, another would write, “I can’t find my favourite sneakers.”
Lisa Poisso (2017), remarked, “For an everyday Joe, mixing English usage from all parts of the world creates no issues. If you like the way the Brits spell theatre, go for it; countless American theaters seem to think it looks more elegant and do exactly that.”
When Not to Mix British English and American English
There are a number of cases when mixing the two language versions is not considered to be very impressive.
1. Academic Papers
Being consistent is an important factor in terms of professional writing skills. When writing up a school or a university report, you would want to choose one version and stick to it. Since your lecturer is an academic, he or she would notice when your writing style depicts inconsistency. This could decrease your marks.
2. When Writing a Book and / or Novel
According to Louise Harnby (2017), our preferences and nuances come second, because when it comes to novel craft, it’s always all about your reader. So unless you are quoting different characters, do not mix the two. Amazon has been known to have discarded a number of books for sale due to inconsistent language used by the authors.
3. When Addressing People from a Regional Area
If you were to prepare a speech for an audience in the US, it would be a good idea to prepare it in American English. While this may not be compulsory, it would indeed make a good impression to a few key people. It would also do away with potential misunderstandings and confusion. While some people in North America may know what an “aubergine” is, others might not. Use the term “eggplant” instead.
It is worth noting that the two (British English and American English do not compete one against the other. Lisa Brown (2019) rightly remarked that, “One is not necessarily better than the other, but instead used when needed.”