approval vs backup

approval and backup both are nouns.

Word	Noun	Adjective	Verb	Adverb
approval	Yes	No	No	No
backup	Yes	No	No	No

As nouns, backup is a hyponym of approval; that is, backup is a word with a more specific, narrower meaning than approval:

approval (noun)	backup (noun)
the formal act of approving	the act of providing approval and support
a message expressing a favorable opinion	(computer science) a copy of a file or directory on a separate storage device
a feeling of liking something or someone good	a musical part (vocal or instrumental) that supports or provides background for other musical parts
acceptance as satisfactory	someone who takes the place of another (as when things get dangerous or difficult)
	an accumulation caused by clogging or a stoppage