letter vs let

letter and let both are nouns.

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

letter (noun)	let (noun)
a written message addressed to a person or organization	a serve that strikes the net before falling into the receiver's court; the ball must be served again
the conventional characters of the alphabet used to represent speech
an award earned by participation in a school sport
a strictly literal interpretation (as distinct from the intention)
owner who lets another person use something (housing usually) for hire

letter (verb)	let (verb)
mark letters on or mark with letters	leave unchanged
set down or print with letters	cause to move; cause to be in a certain position or condition
win an athletic letter	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