unbeknownst vs unbeknown

unbeknownst and unbeknown both are adjectives.

Word	Noun	Adjective	Verb	Adverb
unbeknownst	No	Yes	No	Yes
unbeknown	No	Yes	No	Yes

As adjectives, unbeknownst and unbeknown are synonyms defined as:

unbeknownst and unbeknown: (usually used with `to') occurring or existing without the knowledge of

As adverbs, unbeknownst and unbeknown are synonyms defined as:

unbeknownst (adjective)	unbeknown (adjective)
(usually used with `to') occurring or existing without the knowledge of	(usually used with `to') occurring or existing without the knowledge of

unbeknownst (adverb)	unbeknown (adverb)
without someone's knowledge	without someone's knowledge