6 Key Differences Between U.S. and U.K. English

Do you work more with clients who use U.S or U.K. English? Which one is primarily used in your workplace? U.S. and U.K. English differ in a number of respects. You need to be aware that when writing, these differences determine your style in the eyes of readers. The following is a guide to help you identify some of the most common U.S./U.K. variations.

That and Which

A restrictive clause is a set of words you cannot remove without changing the meaning of a sentence. For example, in “John expressed a view that Monica thought was unacceptable,” the restrictive clause is “that Monica thought was unacceptable.” In U.K. English, you may employ “that” or “which” to introduce such a clause. In U.S. English, you may use only “that.” Further, a non-restrictive clause is a set of words that introduces information into a sentence. A comma precedes this clause and follows it. For example, in “The region, which is uninhabitable, is mainly desert,” the non-restrictive clause is “which is uninhabitable.” Here, both U.S. and U.K. English use “which” and not “that.”

Quotation Marks

Quotation marks are either single or double. U.S. English uses double quotation marks at the beginning and end of a quotation. It then uses single quotation marks for a quotation that appears within a quotation. For example: “What you refer to as ‘a modern plague’ has struck again.” U.K. English reverses this approach: ‘What you refer to as a “modern plague” has struck again.’ There are two points worth noting about quotation marks, though. First, U.K. newspapers often follow U.S. usage. Second, those who write for the internet tend to follow U.K. practice because single quotation marks are clearer on a screen.


U.S. English presents dates in month, day, year order with a comma after the day. For example: January 5, 1892. U.K. English arranges dates in day, month, year order without any comma. For example: 5 January 1892.


Punctuation in U.S. and U.K. English differs in numerous ways. The following is a summary.

  • In U.S. English, the word that follows a colon has an initial capital letter when the colon introduces a sentence that is grammatically complete. U.K. English only capitalizes the initial letter of a word that follows a colon if the word is a name.
  • For business correspondence, U.S. English places a colon after the greeting. Thus: “Dear Sir:” U.K. English uses a comma rather than colon.
  • A “period” in U.S. English is a “full stop” or “full point” in U.K. English.
  • An “exclamation point” in U.S. English is an “exclamation mark” in U.K. English.
  • In U.S. English, a period follows contractions of words such as “Dr.” U.K. English, however, omits the period.
  • U.S. English places a comma after “e.g.” and “i.e.” For example, “He ate numerous vegetables, e.g., spinach, peas, and carrots.” In U.K. English, a comma does not follow “e.g.” and “i.e.”


U.S. English prefers to combine a prefix, such as “non,” with the word that follows. For example, “nonnegotiable,” “reentry,” and “preeminent.” U.K. English uses a hyphen between the prefix and the following word. Thus: “non-negotiable,” “re-entry,” and “pre-eminent.” But even in U.S. English, a hyphen is sometimes necessary to ensure that the sense of a word is clear. For example, “anti-intellectual.” If in doubt, consult a dictionary.


Spelling in U.S. and U.K. English can vary in ways that sometimes involve merely a change or omission of just one letter. For instance, U.S. English often employs “o” as opposed to “ou,” “e” as opposed to “oe” or “ae,” “og” as opposed to “ogue,” and “or” as opposed to “our.” In the following examples, the U.S. English version of each word is the first:

  • “moldy” and “mouldy”
  • “ameba” and “amoeba”
  • “toxemia” and “toxaemia”
  • “catalog” and “catalogue”
  • “neighbor” and “neighbour”

Other variations are the U.S. English preference for “z” as opposed to “s,” “k” as opposed to “c,” “f” as opposed to “ph,” “er” as opposed to “re,” and “ense” as opposed to “ence.” Examples are as follows, with the U.S. English version of each word given first:

  • “paralyzed” and “paralysed”
  • “skeptical” and “sceptical”
  • “sulfur” and “sulphur”
  • “theaters” and “theatres”
  • “offense” and “offence”

U.S. English also uses a double rather than single “l” in words such as “enrollment.”

U.S. and U.K. English are similar languages, but with their own characteristics. The overall sense in both is generally the same; however, the differences matter in business, academia, and other formal environments. Use the foregoing guide to avoid confusion and error.