tub vs vat

tub and vat both are nouns.

Word	Noun	Adjective	Verb	Adverb
tub	Yes	No	No	No
vat	Yes	No	No	No

As nouns, tub and vat are synonyms defined as:

tub (noun)	vat (noun)
a large open vessel for holding or storing liquids	a large open vessel for holding or storing liquids
a relatively large open container that you fill with water and use to wash the body
the amount that a tub will hold