“Supposedly” vs. “Supposably”: Yes, There Is A Difference

Recently, we added the word supposably to our dictionary. And, what do you suppose happened?

For one thing, we discovered how strongly people feel about this word—which many assume to be a recently invented term or a mispronunciation. Others quite reasonably think it’s a synonym of supposedly. After all, even Joey from Friends famously and hilariously couldn’t figure out if supposedly and supposably were different words.

Here’s the shocking truth: supposably is, in fact, a real word and has been used since at least the 1700s. However, it may not mean quite what you (or Joey) think it does. To celebrate supposably’s new entry in our dictionary, let’s break down the difference between the words supposably and supposedly.

What does supposedly mean?

Let’s start with the word most people know. The word supposedly means “according to what is accepted or believed, without positive knowledge.”

Supposedly is an adverb based on the word supposed. Supposedly is used to express doubt that something is what people say it is. It is a synonym of the word allegedly.

The word supposedly is used when a person has heard information about something, such as from the news or the rumors going around town. At the same time, they aren’t sure if the information is actually true. For example, a person may say that the dinosaurs are supposedly extinct if they don’t believe the dinosaurs are really gone. Maybe they’re hiding in a theme park somewhere?

What does supposably mean?

Supposably means “as may be assumed, imagined, or supposed.”

Supposably is an adverb based on the word supposable. If something is supposable, it means that it is possible or conceivable. Therefore, supposably is a synonym of the adverbs possibly and conceivably. If something can supposably happen, it means it is within the realm of possibility that it can happen. It is often used with words such as might, may, or could.

For example, it is correct to say that a dog may supposably be friends with a cat. Although they usually don’t get along, there is plenty of evidence of cats tolerating dogs. On the other hand, it would be incorrect to say that pigs could supposably fly. Pigs do not have wings nor the money to pay for flight school. Because a pig flying is impossible, logically you wouldn’t say that a pig may supposably fly—unless you fitted them with wings.

Strapping a pig with wings could be torturous, for both you and the pig. Which leads us to another discussion, what’s the difference between torturous and tortuous?

How to use supposedly and supposably

The easiest way to know which word you should use is to see if you want to say that something is supposed to be a certain way or if it is possible for something to be a certain way.

For example, if someone says that a particular bug spray supposedly kills mosquitoes, they are doubtful of the truth of this advertised claim—and are probably being munched on by mosquitoes!

On the other hand, if someone says that a particular bug spray supposably kills mosquitoes, they are saying that it is possible that the bug spray could kill mosquitoes—it is made from a chemical that can be lethal to mosquitoes.

Here are some more examples of correct uses of supposedly and supposably:

• My son supposedly bathed the dog but she smells like a dumpster!
• Although it is very unlikely, a skydiver could supposably survive jumping out of an airplane without a parachute.
• “Supposedly, the Egyptians built the pyramids,” Stan said. “If you ask me, it was time-traveling robots!”
• They set the betting odds at a million to one, which means that they believe that the celebrity chef might supposably defeat the professional boxer in a boxing match somehow.

So, here’s the big idea:

While supposably is a real (if rare) word, most people will opt for synonyms such as possibly or conceivably. Because many mistakenly believe others using supposably is a mistake, a lot of people avoid supposably so as not to invoke the wrath of people who are supposedly grammar snobs.