yowl vs bellow

yowl and bellow both are nouns.

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

As nouns, yowl and bellow are synonyms defined as:

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

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

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