authorise vs let

authorise is not a noun while let is a noun.

Word	Noun	Adjective	Verb	Adverb
authorise	No	No	Yes	No
let	Yes	No	Yes	No

As verbs, let is a hypernym of authorise; that is, let is a word with a broader meaning than authorise:

Other hypernyms of authorise include allow, countenance, permit.

authorise (noun)	let (noun)
	a serve that strikes the net before falling into the receiver's court; the ball must be served again

authorise (verb)	let (verb)
grant authorization or clearance for	leave unchanged
give or delegate power or authority to	cause to move; cause to be in a certain position or condition
	actively cause something to happen
	consent to, give permission; permit
	grant use or occupation of under a term of contract
	make it possible through a specific action or lack of action for something to happen