equid vs mule

equid and mule both are nouns.

Word	Noun	Adjective	Verb	Adverb
equid	Yes	No	No	No
mule	Yes	No	No	No

As nouns, mule is a hyponym of equid; that is, mule is a word with a more specific, narrower meaning than equid:

equid: hoofed mammals having slender legs and a flat coat with a narrow mane along the back of the neck
mule: hybrid offspring of a male donkey and a female horse; usually sterile

Other hyponyms of equid include Equus caballus, horse, ass, hinny, zebra, Equus quagga, quagga.

equid (noun)	mule (noun)
hoofed mammals having slender legs and a flat coat with a narrow mane along the back of the neck	hybrid offspring of a male donkey and a female horse; usually sterile
	a slipper that has no fitting around the heel