Other forms: plausibilities
Something's plausibility is how likely it is to be true. You might, for example, question the plausibility of your brother's story about seeing a UFO land in the back yard.
The noun plausibility means "likelihood" or "believability." You're most likely to come across the word in a negative or questioning context, as when someone doubts the plausibility of an action movie's plot or questions the plausibility of a debater's claims and arguments. If you aren't sure you believe something, you'll question its plausibility. The Latin root is plausibilis, "deserving applause or acceptable."