Although British and American English are (for the most part!) mutually comprehensible, there are nevertheless many lexical differences between them, some subtle, others quite stark and still others potentially problematic. Lists of these differences abound on the internet. For a handy example that groups many of the most common ones thematically, see British and American synonyms for the IELTS by Portland English Language Academy. For an alphabetical list of some of the most common culprits, see American English to British English Vocabulary at ThoughtCo. Voice of America offers a more humorous take in its segment American English vs. British English.

In keeping with its preference for English tailored to an international audience, the UOC recommends avoiding terminology that is so specific to a given place, country or variety of English as to be confusing or directly opaque to speakers of other varieties and non-native speakers. Wherever possible, it encourages the use of more internationally familiar options, instead.