impossibility vs impossible action

impossibility and impossible action both are nouns.

Word	Noun	Adjective	Verb	Adverb
impossibility	Yes	No	No	No
impossible action	Yes	No	No	No

As nouns, impossibility and impossible action are synonyms defined as:

impossibility and impossible action: an alternative that is not available

impossibility (noun)	impossible action (noun)
an alternative that is not available	an alternative that is not available
incapability of existing or occurring