probably vs plausibly

probably and plausibly both are adverbs.

Word	Noun	Adjective	Verb	Adverb
probably	No	No	No	Yes
plausibly	No	No	No	Yes

As adverbs, probably and plausibly are synonyms defined as:

probably and plausibly: easy to believe on the basis of available evidence

Other synonyms of probably include believably, credibly.

probably (adverb)	plausibly (adverb)
with considerable certainty; without much doubt	easy to believe on the basis of available evidence
easy to believe on the basis of available evidence