Although each of these words is used to refer to a value that is estimated and therefore imprecise, whether it is acceptable to use them interchangeably depends in part on context and the level of accuracy being implied.
Some speakers and writers will use approximately before turning to the other two—not surprising, because people faced with a choice between words will often choose the most impressive-sounding one. And sometimes that choice happens to be correct. On the other hand, people will often, especially in casual communications, use around or about as a sort of verbal shorthand. And again, sometimes that choice happens to be correct.
So, what’s the scoop? To sort this out, it helps to recognize that authorities for the most part agree that around, about, and approximately lie on a scale from casual to formal. As it happens, around is also thought of as the most imprecise and approximately the most precise, with about falling somewhere in between. It further helps to note that around, meaning merely “with some approach to exactness,”1(p68) is not widely considered an adequate replacement for either about or approximately and thus is often accepted only in casual conversation.2 Hence, in conversation between friends, for example, many speakers will toss off a “See ya around three,” whereas in written communications, as Bernstein maintains, “‘about three o’clock’ is preferable to ‘around three o’clock.’”2
Things get a bit more complicated as one moves along the scale: not only does the choice of word depend in part on the closeness to accuracy required by different types of communication, but the differences between the implied degrees of closeness can be subtle. For example, Merriam-Webster’s defines about as “reasonably close to”1(p4) and approximately as “nearly correct or exact.”1(p61) However, it is safe to say that in nontechnical communications (which presumably often place less emphasis on precision), the use of about is not only accepted but is perhaps preferred. As Garner maintains, “When possible, use about instead of approximately, a formal word”3(p5)—where a “formal” word is defined simply as one “occupying an elevated level of diction.”3(pp153-154) On the other hand, as suggested by the above definitions, about does not emphasize a closeness to accuracy as strongly as approximately does—which helps explain why about seems fine when used to refer to estimated values that have been rounded to multiples of 5 or 10 but can seem strange when used to refer to unrounded values.4 Moreover, around and about each have multiple meanings and can be used in other senses, whereas approximately is used in a single sense only, leading some authorities to maintain that the latter is a better choice for technical communications.5
The bottom line:
● Referring to an inexact value in casual conversation? Around, about, and approximately are all acceptable, but approximately can sound a bit pretentious.
● Referring to an inexact value in nontechnical writing? About is perhaps the best choice, around being too informal and approximately being a tad too formal.
● Referring to an inexact value in medical or other technical writing? Although about may very occasionally be used if one carefully assesses the context, approximately is nearly always the best choice.—Phil Sefton, ELS
1. Merriam-Webster’s Collegiate Dictionary. 11th ed. Springfield, MA: Merriam-Webster Inc; 2003.
2. Around. In: Bernstein TM. The Careful Writer: A Modern Guide to English Usage. New York, NY: Athaneum; 1985:44-45.
3. Garner BA. The Oxford Dictionary of American Usage and Style. New York, NY: Oxford University Press; 2000.
4. Yateendra J. About and Around and Approximately: Shades of Difference? Editage website. http://blog.editage.com/about-and-around-and-approximately-shades-of-difference. Accessed August 1, 2012.
5. Scientific English as a Foreign Language: Around, About, Approximately. Worcester Polytechnic Institute website. http://users.wpi.edu/~nab/sci_eng/97_Jun_20.html. 1997. Accessed August 1, 2012.