barrel vs tun

barrel and tun both are nouns.

Word	Noun	Adjective	Verb	Adverb
barrel	Yes	No	Yes	No
tun	Yes	No	No	No

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

barrel: a cylindrical container that holds liquids
tun: a large cask especially one holding a volume equivalent to 2 butts or 252 gals

Other hyponyms of barrel include beer barrel, beer keg, butt, hogshead, keg, pickle barrel, shook, wine barrel, wine cask.

barrel (noun)	tun (noun)
a cylindrical container that holds liquids	a large cask especially one holding a volume equivalent to 2 butts or 252 gals
a tube through which a bullet travels when a gun is fired
any of various units of capacity
the quantity that a barrel (of any size) will hold
a bulging cylindrical shape; hollow with flat ends

barrel (verb)	tun (verb)
put in barrels