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Would anyone kindly explain the difference between these?

  • Possible

  • Probable

I have searched dictionaries and on all over the Internet, but I have not been able to understand yet what the difference is!

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what's the confusion? which definitions you got? What did you understand from them? –  Maulik V Apr 13 at 8:39
    
What is the difference between 'impossible' and 'improbable'? –  Nico Apr 13 at 8:41
    
I can not understand the difference between IMPROBABLE AND IMPOSSIBLE. Moreover, I can not understand the difference between POSSIBLE AND PROBABLE too. –  nima_persian Apr 13 at 9:00
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Nice question! Your question is pretty deep also if we consider the technical meaning of probability and possibility. For example even if we define "probable" as "having probability bigger than 0", still probable != possible and improbable != impossible, because events that have probability 0 can be possible (e.g. guessing correct lottery number from a lottery that uses the whole natural number set). Possible/Impossible only related to the existence of such event, while probable/improbable can define the likelihood that the event. –  Bakuriu Apr 13 at 12:43
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Most Likely: Probable > Possible > Improbable > (Impossible = will not happen). –  Phil Apr 14 at 1:10

9 Answers 9

up vote 11 down vote accepted

The specific percentage probabilities depend on context but in short;

  • Possible means it can happen, (be it unlikely or likely - however it is more often used for things which are unlikely)
  • Probably means it is likely to happen

Related terms;

  • Definite means it will happen.
  • Improbably means it could happen but it is unlikely
  • Impossible means it cannot happen

Use of probable or possible for things which are definite

It would feel very unnatural (and give the wrong meaning) to say that something definite was probable or possible and should be avoided. For example I would say "it is definite that I am using a computer to type this" not "it is probable I am using a computer to type this". This is because the strongest term should be used to describe the likelihood

However; when used as a condition it becomes acceptable. For example "If it is possible that it will be sunny tomorrow we will go to the park" or "If it is probable that it will be sunny tomorrow we will go to the park", if the weatherman gives a forecast of 100% chance of sun then you still go to the park.

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+1 I love the visualization here. Coupla minor thoughts: 1) The order seems semi-randoml I'd go from definite to impossible, with possible in the middle. 2) There seems to be an asymmetry at the extremes - I'd expect improbable and possible to touch the bottom in the same way possible and probably touch the top. (See what you get for giving us such a cool inch? Demands for feet!) –  Jaydles Apr 14 at 19:15
    
@Jaydles (1) completely agree, I'll fix that when I'm next on PC. (2) I let possible and probable touch the top (with a dashed background) because of what I was saying in my last paragraph. That arguably definately is a subcategory of possibly. I'm not really happy about that because its very context dependant. I'll have a think –  Richard Tingle Apr 14 at 21:47
    
I feel like I keep doing this on ell and English usage, but "It would feel very unnatural (and give the wrong meaning) to say that something definite was probable or possible and should be avoided" is yet another rule that is commonly broken ironically. So if we (especially in the UK) say, "it's possible that we have a tiny problem here", or "you probably don't want to do that", then we mean, "we have a serious problem", and "don't do that". So: you probably don't want to break the rule yourself until you get the hang of it, but possibly you should be receptive to others breaking it ;-) –  Steve Jessop Apr 15 at 0:18

In the NFL, injured players get listed week-to-week on an injury report, and each player gets of these statuses:

Probable: a 75% likelihood that the player will play
Questionable: a 50% likelihood that the player will play
Doubtful: a 25% likelihood that the player will play
Out: the player will not play

If an event is probable, there is better than a 50-50 chance that it will happen, although the word is usually reserved for something “comfortably above” a 50-50 chance. In other words, if I had 100 balls in a hat, and 52 of them were pink, and 48 of them were blue, I don't think I'd say, "I will reach in, and I will probably pull out a pink one." However, I might use probable if 67 balls were pink, and 33 were blue, and I'd be even more likely to say it if there were 90 pink balls and 10 blue ones).

The more likely an event will happen, the more suitable the word probable becomes.

On the other hand, possible means that there is a non-zero chance something will happen; it's used for a wider range of probabilities. For example, back to the bin with 90 pink balls, and 10 blue ones; I could say:

It's probable that I will pick a pink ball, although it's possible I will pick a blue one.

However, possible can be used even for probabilities over 50%. If a meterologist's weather model indicates a 60% chance of rain on Friday, a weather forecaster might say:

Temperatures will get cooler on Friday; rain is possible.

At some point (probably around 70% or so, although this is not something that is precisely defined), probable becomes a better word than possible. For example, if the weather model shows an 80% chance of rain, the forecaster might instead say:

Temperatures will get cooler on Friday; rain is likely.

(Likely and probable are synonyms in this context.)

Another way to look at it would be: All things that are probable are possible, but not all things that are possible are probable. Today, many things could happen to me: I could be attacked by a shark, struck by lightning, hit by a car, or take a walk. All of those are possible, but only one is probable.

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Regarding the weather forecaster and probabilities, there is a joke: “What is the probability the weather you forecast to happen?” asked the reporter. “About 40%” answered the weather forecaster. “Why, then you don’t say vice versa”, replied the reporter. –  Lucian Sava Apr 14 at 6:22
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Regarding improbable and impossible: If the are 90 pink balls, and 10 blue balls, it is improbable that you will pick a blue one (and as such, probable that will pick a pink one). However, it is impossible that you would pick a green one, as that one isn't available for you to pick. –  Tiberia Apr 14 at 8:07

Probable means it's likely to happen. Possible means it could happen, but not necessarily likely.

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This says it very nicely in a nutshell. –  J.R. Apr 14 at 10:01

Used on its own, "probable" means an event is very likely but not absolutely certain, without attaching a specific numerical probability. Similarly, "possible" means an event is not impossible, but says nothing about the numerical probability of the event being considered. Numerical probabilities can be used alongside the terms "probable" and "possible" but these will vary depending on the sort of risk being considered, and interpretation often depends on subjective judgements. In any case, once you specify numerical probabilities, the terms "probable" and "possible" really become redundant.

EG: "It is probable that a Cabinet Minister found guilty of unacceptable behaviour will resign in the following week, but anything is possible." "It is possible that it will be dry on any day in the year in London but it is probable that it will rain there on at least one day in October." "It is possible that you will be killed crossing the road in London but probable that you will reach the other side safely if you obey the signs and keep your wits about you."

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Possible: The probability of this happening is greater than zero. Antonym: impossible.

Probable: The probability of this happening is greater than 50%. Synonym: likely. Antonyms: improbable, unlikely.

It is possible that we will all be killed tomorrow by a solar flare, but it is extremely improbable.

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When an event is probable, it is more likely to occur than if it were just possible. For example, it is possible that England will win the World Cup but it is probable that Brazil will.

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I don't think this is a good example. Some people could argue that it is impossible that England will win the World Cup! (Nico runs away and hides) –  Nico Apr 13 at 12:32
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Haha! It impossible for Sweden to win the World Cup because they didn't qualify; but it is possible for England to win it because they have not been eliminated yet! Whatever you may think! –  KCH Apr 13 at 12:38
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Curse Gordon Banks's stomach ailment... –  BobRodes Apr 13 at 19:04
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p. s. If I may mention it, it is also possible that the US will win the World Cup. :) –  BobRodes Apr 13 at 19:07
    
Yes, correct, almost everything is possible. Yet few are probable, if any. –  Lucian Sava Apr 14 at 6:27

Possible means that an event can occur under the given circumstances.
Probable means that an event is likely to occur under the given circumstances.

If something is impossible, it is necessarily improbable. If an event cannot happen, it is unable to occur likely.

But a possible event can be not probable. Say you observe me eating eggs and you make a mental note. Then you might assume that it is very unlikely that I ever eat more than 3 eggs. You can watch for a lifetime and very probably my egg consumption will never exceed 3 eggs at a time.

But if you put a 1 kg gold ingot before me on the table and tell me: "Eat 10 eggs and you win this ingot", then you will see that it is possible for me to eat 10 eggs.

It is not probable that an nuclear power station will blow up under normal circustances. But it is entirely possible to blow up a nuclear power station if you or the systems screw up.

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“No one can eat 50 eggs” :^) –  J.R. Apr 14 at 1:18

It's a matter of degrees that something will happen. Something that is possible is not necessarily probable, while something that is probable is more than possible. Probable would imply that something has more than 50% or higher of happening while Possible means that something could happen at varying degrees of certainty from 1% to 99% , because 0% would be absolutely not and 100% would be absolutely yes. So possible would mean 1% to 99% while probably would mean greater than 50% of happening.

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Possible - something can happen. Probable - something can happen, and there is a good chance of it happening.

However...

Impossible - something cannot happen. Improbable - something can happen, but there is a good chance of it not happening.

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