donkey vs ass

donkey and ass both are nouns.

Word	Noun	Adjective	Verb	Adverb
donkey	Yes	No	No	No
ass	Yes	No	No	No

As nouns, ass is a hypernym of donkey; that is, ass is a word with a broader meaning than donkey:

donkey: domestic beast of burden descended from the African wild ass; patient but stubborn
ass: hardy and sure-footed animal smaller and with longer ears than the horse

donkey (noun)	ass (noun)
domestic beast of burden descended from the African wild ass; patient but stubborn	slang for sexual intercourse
the symbol of the Democratic Party; introduced in cartoons by Thomas Nast in 1874	hardy and sure-footed animal smaller and with longer ears than the horse
	the fleshy part of the human body that you sit on
	a pompous fool