Possible means capable of happening — a statement about reality. Plausible means it sounds believable — a statement about how convincing something seems. The two come apart constantly: winning the lottery is possible but not plausible, and a well-told lie is plausible but not true.
The core difference
Possible describes the world; plausible describes an impression. That gap is the whole point of keeping them separate.
The four combinations
- possible and plausible — The train is delayed by weather.
- possible but implausible — The train is delayed by a meteor strike.
- plausible but false — a confident, coherent explanation that turns out to be wrong.
- neither — The train arrived yesterday tomorrow.
Why plausible carries a warning
Plausible has a long undertone of "convincing on the surface". Describing an account as plausible is not the same as endorsing it, and in careful writing it often signals mild reservation: it holds together, and that is all we know.
Choosing
If you mean it could occur, write possible. If you mean it sounds credible, write plausible. If you mean it is likely, neither word will do — write probable.
