Supposedly vs. Supposably

Have you ever heard someone use the word supposably and wondered what they meant? Maybe it’s a synonym for supposedly? Or a mistake? Supposedly and supposably are often confused, perhaps most famously by Joey from Friends. Both of these words come from the English word suppose, which is a combination of sup- (a variant of sub- meaning “slightly,” “imperfectly,” “nearly”) and pose meaning “to assert, state, or put forward.” Supposedly predates supposably by more than 100 years. What is the difference between these two words today?

Supposedly is an adverb that means “according to what is accepted or believed to be true; seemingly, purportedly.” It is typically used when someone wants to convey doubt, as in this recent op-ed from the New York Times: “The other risk, raised by some City Council members and advocates for the poor and working class, is that supposedly ‘affordable’ rents can still be too high for too many struggling New Yorkers.”

Though the strict grammarians at BuzzFeed have lamented that our world is ending because so many people use supposably, it is a valid word that is recorded in several dictionaries of English, including Dictionary.com. However, it has historically carried a slightly different meaning than supposedly; supposably means “conceivably.” Most people use it interchangeably with supposedly, which is technically incorrect (despite the fact that the meaning is typically understood).

In this 1845 example, the author considers scenarios in which a parent’s authority may be revoked: “The only justifiable, or supposeably proper, occasion for taking this business out of the hand of the parent […] is, that he will not attend to it […]. This is a case which may be supposed.”

In our research, we encountered a strange and extreme spike in the use of the word supposably between the 1860s and the 1930s in Google Ngram. This word never came close to the usage volume as supposedly, but the trend is notable.

Which one should you use? Since there is much ado about supposably and its meaning is very specific, we recommend that you stick with supposedly.

Where do you stand on the use of supposably?