weakness vs failing

weakness and failing both are nouns.

Word	Noun	Adjective	Verb	Adverb
weakness	Yes	No	No	No
failing	Yes	Yes	No	No

As nouns, weakness and failing are synonyms defined as:

weakness (noun)	failing (noun)
the property of lacking physical or mental strength; liability to failure under pressure or stress or strain	failure to reach a minimum required performance
powerlessness revealed by an inability to act	a flaw or weak point
a penchant for something even though it might not be good for you
a flaw or weak point
the condition of being financially weak

weakness (adjective)	failing (adjective)
	below acceptable in performance