permission vs approval

permission and approval both are nouns.

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

As nouns, approval is a hypernym of permission; that is, approval is a word with a broader meaning than permission:

Other hypernyms of permission include commendation.

permission (noun)	approval (noun)
the act of giving a formal (usually written) authorization	the formal act of approving
approval to do something	a message expressing a favorable opinion
	a feeling of liking something or someone good
	acceptance as satisfactory