bellow vs yowl

bellow and yowl both are nouns.

Word	Noun	Adjective	Verb	Adverb
bellow	Yes	No	Yes	No
yowl	Yes	No	Yes	No

As nouns, bellow and yowl are synonyms defined as:

Other synonyms of bellow include bellowing, holla, holler, hollering, hollo, holloa, roar, roaring.

bellow (noun)	yowl (noun)
a very loud utterance (like the sound of an animal)	a very loud utterance (like the sound of an animal)

bellow (verb)	yowl (verb)
shout loudly and without restraint	utter shrieks, as of cats
make a loud noise, as of animal	cry loudly, as of animals