howl vs yell

howl and yell both are nouns.

Word	Noun	Adjective	Verb	Adverb
howl	Yes	No	Yes	No
yell	Yes	No	Yes	No

As verbs, yell is a hypernym of howl; that is, yell is a word with a broader meaning than howl:

Other hypernyms of howl include call, cry, holler, hollo, scream, shout, shout out, squall.

howl (noun)	yell (noun)
a long loud emotional utterance	a loud utterance; often in protest or opposition
a loud sustained noise resembling the cry of a hound	a loud utterance of emotion (especially when inarticulate)
the long plaintive cry of a hound or a wolf

howl (verb)	yell (verb)
laugh unrestrainedly and heartily	utter or declare in a very loud voice
make a loud noise, as of wind, water, or vehicles	utter a sudden loud cry
emit long loud cries
cry loudly, as of animals