Application of Cannot and Can Not | Usage Tips

Cannot and can not are technically the same. The closed form is most common and usually considered correct. However, there are instances of when can not (yes, two words) is preferred. This is what I’ll get into today. Along with today’s topic, I’ll also introduce some information related to comma usage. I encourage everyone to read more on the subject through the resources included at the end.

Cannot and Can’t

A common argument is that contractions shouldn’t be used in formal/academic writing. However, in practice, contractions are actually commonly used. Use your best judgment on whether the contraction would be accepted as proper for the context in which you are writing. This means that both cannot and can’t can be used interchangeably in most circumstances to negate can, an auxiliary verb used to indicate being able to do something or show knowledge or a possibility. The following two sentences have the same meaning and equally appropriate in most circumstances.

Example I: She cannot go to the conference due to other obligations.

Example II: She can’t go to the conference due to other obligations.

Can Not

The open form, can not, is generally not preferred.

Example: She can not go to the conference due to other obligations.

Yes, it is technically correct but not a recommended form. While correct in the strictest sense, experts encourage writers to avoid such a construction. Sabin (2010, 126) says “cannot should not appear as two words, except in the rare instances when not is part of another construction.” Using an open form will raise red flags and possibly lessen your credibility as a writer. Avoiding the open form is usually a best practice, but what does Sabin mean by instances when not is part of another construction? One of the best examples is when not functions as an essential component of a phrase, such as not only… but also.

Example I: She can not only sing but also dance.

Example II: We can not only see the show but also go for dinner.

Merriam-Webster (n.d.) has a test to see whether the two-word form would work. Essentially, if the sentence works with can’t, then use the closed form; otherwise, use the open form.

Example: She can’t only sing but also dance. ?

In the above example, can’t doesn’t work, so the preferred form would be can not.

Can We or Can We Not Use a Comma

(As an aside, the section title also shows another instance of splitting can and not.)

According to Chicago (2017, 385), commas are usually not necessary with phrases like not… but and not only… but also. Most other style manuals are silent on the matter. However, Oxford (2014); Christiansen, Iverson, Flanagin, et al. (2020); Walsh (2000); and others follow the Chicago style throughout their publications even if they don’t have prescriptive rules.

Conversely and curiously enough the Associated Press (2020) includes no fewer than seven instances of not… but constructions, and they all include commas. I see this as a curiosity since their stance on serial commas is supposed to be related to saving space for print publications. (See previous article on serial commas: https://www.dhirubhai.net/pulse/serial-commas-usage-tips-michael-peterson/.) So including obviously unnecessary commas in this case seems to contradict the reasoning for avoiding the serial comma. The Economist (2018) is also contradictory in usage. There are two instances of not… but constructions; one has a comma while the other does not.

Conclusion

Generally speaking, cannot is largely considered the proper form, so use it. If you are unsure about whether the closed or open form would work best, use the “can’t test.” You can also pretty much ditch the comma with not only... but also constructions.

References

The Associated Press Stylebook 2020–2022. 55th ed. 2020. New York: Basic Books.

The Chicago Manual of Style. 17th ed. 2017. Chicago: University of Chicago Press.

Christiansen, Stacey, Cheryl Iverson, Annette Flanagin, et al. 2020. AMA Manual of Style: A Guide for Authors and Editors. 11th ed. New York: Oxford University Press; 2020.

The Economist Style Guide. 12th ed. 2018. London: Profile Books, Ltd.

Merriam-Webster. n.d. “‘Cannot’ vs. ‘Can Not’: Is There a Difference?” Accessed May 2, 2022. https://www.merriam-webster.com/words-at-play/cannot-vs-can-not-is-there-a-difference.

New Hart’s Rules: The Oxford Style Guide. 2nd ed. 2014. New York: Oxford University Press.

Sabin, William. 2010. The Gregg Reference Manual: A Manual of Style, Grammar, Usage, and Formatting—Tribute Edition. 11th ed. New York: McGraw-Hill.

Walsh, Bill. 2000. Lapsing into a Comma: A Curmudgeon's Guide to the Many Things That Can Go Wrong in Print—and How to Avoid Them. New York: McGraw-Hill.