betray vs fail

betray and fail both are verbs.

Word	Noun	Adjective	Verb	Adverb
betray	No	No	Yes	No
fail	No	No	Yes	No

As verbs, betray and fail are synonyms defined as:

betray (verb)	fail (verb)
give away information about somebody	stop operating or functioning
reveal unintentionally	deteriorate
cause someone to believe an untruth	prove insufficient
disappoint, prove undependable to; abandon, forsake	disappoint, prove undependable to; abandon, forsake
deliver to an enemy by treachery	become bankrupt or insolvent; fail financially and close
be sexually unfaithful to one's partner in marriage	be unsuccessful
	fail to get a passing grade
	fail to do something; leave something undone
	judge unacceptable
	be unable
	fall short in what is expected