Plausible vs. Possible: What’s the Difference?

Various nuances in English can be challenging to understand, even for native speakers. For instance, native and second-language speakers sometimes struggle to differentiate between words like “plausible” and “possible” that sound almost identical but have distinct meanings.

The main difference between “plausible” and “possible” is that “plausible” means you could make a reasonably valid case for something, while “possible” means something is capable of becoming true, though it’s not always reasonable.  Both are adjectives, but they also have adverb and noun forms.

Using “plausible” and “possible” as interchangeable could convey just the opposite of what you intend. However, when you understand the distinction, you’ll be able to use either word with confidence. Read on and find out all you need to know about using “plausible” and “possible” correctly in all their forms.

The Origins of Plausible and Possible

When we understand the etymology of the words, the differences in their modern use becomes clearer. Although they both originated in Latin, they have different roots and meanings.

Plausible

The word “plausible” has come to English from the Latin adjective plausibilis, which means “worthy of applause.” Plausibilis is derived from the Latin verb plaudere, meaning “to applaud or to clap” (source).

Thus, when plausibilis was originally used, it was to describe something worth applauding and had a positive connotation before its meaning shifted in the English-speaking world.

Originally, users applied “plausible” with regard to persons, meaning the person was as agreeable or praiseworthy. It could also refer to something that appears to be true, at least on the surface.

The meaning has changed over time, and, nowadays, it can imply that the person is superficially pleasing or persuasive.

During the Cold War period in the US, “plausible” could describe a person, action, or content that seems genuine but was meant to deceive, especially when using the phrase “plausible deniability.” 

Someone who seeks to maintain “plausible deniability” takes advantage of the fact that what they say sounds like it could be true when, in fact, they know that it’s not. They can deny responsibility for an action because their excuse sounds plausible.

Possible

The word possible has also come to English from Latin via Old French and is derived from the Latin word possibilis. In French, posse means “to be able” (source).

“Possible” has always been used to indicate that something is capable of being true or that something can be done. “Possible” involves what can be, while plausible involves what sounds reasonable, even if it may prove later to have been impossible.

Plausible and Possible Usage in Modern English

To make the difference between the words’ meanings clearer, let’s have a look at how the words are defined in dictionaries, grammar books, and other linguistic guidelines.

Both words are frequently used as adjectives, giving detail about a noun. When looking at the two definitions, we’ll start with their use as adjectives and then explore other differences. 

Plausible

If a story is plausible, the word “plausible” (adjective) indicates that the story (noun) is likely to be true, but not necessarily so. 

When the authorities declare that a bomb has been the plausible explanation for a crash, “plausible” indicates that the explanation (noun) is acceptable, but not necessarily the only possible explanation.

The difference is similar to that between something that is valid and something that is true. Something that appears valid might be very convincing, and the argument for it well-thought-out, yet there remains the possibility that it could prove untrue.

Thus, when we use “plausible,” it doesn’t describe something that is definitely “applaudable” or correct. It depicts the information only as to be believable or reasonable, but not necessarily so.

According to Merriam-Webster’s online dictionary, the first known use of “plausible” in English was in 1565 in the context of superficially fair, reasonable, or valuable, with the emphasis on superficially (source).

In modern English, plausible is most often used to indicate something has only an appearance of truth and only seems worthy of approval and acceptance.

It expresses the view that it sounds honest and sincere, especially when trying to trick people (source).

Similarly, according to the Cambridge Dictionary, a plausible person appears to be honest and telling the truth, even if they are not (source).

Other short definitions for plausible are “probably true,” “probably believable,” or “probably realistic.”

The word placement within a sentence could also change its meaning. Let’s look at the sentence, “She plausibly argued that she was innocent.” Here the meaning is that the argument has been delivered believably.

Again, it is not a direct indication of the truthfulness of the argument.  

Let’s now change the sentence to “In the way she argued her case, her innocence is plausible.” The emphasis is now on the content of the argument, meaning she could have been innocent, but, again, not necessarily.

Likewise, in the following sentences, “plausible” conveys the idea that something only has the potential to be true.

  • Although this seems plausible enough, it’s not the full story.
  • This story is becoming less plausible by the day.   
  • You could manufacture a plausible excuse for leaving early.
  • It sounds plausible until you examine it.
  • She could discern no plausible explanation for its disappearance.
  • He did not think it plausible to explain all differences this way.

Antonym: Implausible

The opposite of something plausible is something implausible, meaning fantastic, unbelievable, unconvincing, or inconceivable. While something implausible is not necessarily untrue, it is tough to believe.

Possible

In the sentence “There is a possible cure for the disease,” the adjective “possible” indicates that there is the potential for a cure (noun). Unless you have knowledge to the contrary, this is true.

The word “possible” always means that something is within the limits of ability and capacity. 

One of the main distinctions between possible and plausible is that “possible” indicates ability more than validity. The first known use of “possible” in English was in the 14th century, with the meaning defined as within the limits of ability or capacity.

Another way to define it is that when something is possible, it can be conceived, be done, or occur according to nature, custom, or manners. Something that is possible is naturally able or likely to happen, other circumstances being equal (source).

Some people use “possible” and “likely” interchangeably. However, it is essential to note that there is a slight difference between them as the latter deals more with probability.

When the chances are good that something will happen, even when there is no proof that it will, we often refer to it as “likely.”

In the following sentences, “possible” conveys the message that if circumstances allow it, the subject will reach the outcome. There is a much greater emphasis on whether something can or cannot be.

  • Advances in medicine have made it possible for people to live longer.
  • It’s the only possible conclusion.
  • I’ll be back by Tuesday, if possible.
  • I desire to go on holiday, if possible.
  • It’s still possible to see the marks on the car.
  • A possible route up the mountain is via the West face. 
  • It’s possible for him to do the job.
  • It’s possible that I forgot my keys.

Antonym: Impossible

Something that is impossible simply cannot happen. While it’s important to distinguish between things perceived as impossible and those things that are actually impossible, something that truly is impossible will never happen under any circumstances.

Both Words in the Same Sentence

The following sentence using both words further illustrates the difference between plausible and possible:

Her story on how they had reached the summit from the East face of the mountain sounded plausible to the others, but I knew it was not true because it was only possible to reach the summit via the West face.

Note closely how the story sounded as if it was in the realm of possibility to those with no experience with the summit; in other words, her story sounded plausible.

However, the individual who knew what the summit was actually like could tell that her story was outside the realm of possibility.

opened book on brown table
Image by Pisit Heng via Unsplash

Synonyms

The difference in the meaning of the two words is further revealed by considering their synonyms. Although synonyms are related to the meaning of the given word, it is important to understand that they do not always convey exactly the same nuance.

Plausible and SynonymsMeaning
Plausible Applies to that which appears to be true, reasonable, or valid at first glance, but which may or may not be so. Only in some circumstances does this imply deliberate deception.
SpeciousApplies to that which is superficially reasonable or valid but is actually not so, and there is a strong connotation that it intends to deceive.
ProbableApplies to that which is most likely to be true or likely to occur. It can reasonably but not certainly be expected. Likely but uncertain.
ColorableApplies to that which appears reflective of reality but is deceptive. It’s intended to conceal and does not correspond with reality. Apparently valid, but actually specious.
BelievableApplies to that which is capable of eliciting belief or trust.
Possible and SynonymsMeaning
PossibleApplies to that which is within the limits of ability, capacity, or realization and has the potential to be.
AttainableApplies to that which can be achieved, accomplished, or obtained.
FeasibleApplies to that which is possible, doable, logical, and likely.
WorkableApplies to that which is capable of functioning. It’s able to work and is practicable.
ViableApplies to that which is able to be done or to survive.

The Nouns Plausibility and Possibility

The noun forms of “plausible” and “possible” are “plausibility” and “possibility,” respectively, meaning the state of being either “plausible” or “possible.” 

Plausibility

When someone states that a witness has lied with enough conviction and plausibility that everyone has believed her, the noun “plausibility” indicates the witness has lied in such a way that it was believable, although untrue. 

The following examples of “plausibility” bear a similar meaning:

  • Beware of the plausibility of salesmen.
  • This new evidence lends plausibility to the notion that the money was stolen.
  • Their ideas gain plausibility amongst the unlettered.
  • He still insisted, against all plausibility, that he would become an attorney.

Possibility

When someone has exhausted every possibility to find his stolen car, “possibility” is the noun used in the context that everything that could be done has been done.

Other examples of the use of “possibility”:

  • There is a strong possibility that I will not be going to Europe.
  • Have you considered the possibility that they may be right?
  • My first concept didn’t work, but I thought of a second possibility.
  • Tomorrow holds many possibilities.

The Adverbs Plausibly and Possibly

Both “plausible” and “possible” can also be used as adverbs, and here the basic difference in meaning still remains. Adverbs modify verbs and typically express manner, place, time, frequency, degree, or level of certainty.

Plausibly

If it is said of a person that he has argued very plausibly, the adverb “plausibly” conveys manner, meaning he seems to be very convincing, but there is not enough evidence to determine for sure if they’re telling the truth or not.

The following are a few examples of the use of “plausibly”:

  • The case was presented very plausibly.
  • He argued very plausibly for its acceptance.
  • He argued very plausibly that the claims were true.
  • He talked plausibly before the committee.

Possibly

On the other hand, if it is said that someone has all the money she can possibly use, the adverb “possibly” confirms the level of certainty.

Other examples of the use of “possibly”:

  • He couldn’t possibly succeed.
  • It may possibly be fine tomorrow.
  • I cannot possibly complete the task by Monday.
  • He can’t possibly complete the form by himself.

Possibly is an adverbial of probability used to show how certain we are (source). For information on the adverbial of probability “definitely,” read “Most Definitely: Possible Ways to Meaningfully Use the Phrase.”

Street Sign, Note, Direction, Possible, Opportunity
Image by Gerd Altmann via Pixabay 

Final Thoughts

Be careful when using a word that sounds almost identical to another, as you may convey exactly the opposite of what you intend to say. Before using an “unknown” word, first, make sure of its meaning.

Excellent sources to use when in doubt are The Oxford New Essential Dictionary and Dreyer’s English. Both can be purchased on Amazon.

Just remember that if something is plausible, it sounds reasonable, whereas something is possible if it’s capable of coming to pass.

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