race horse vs Equus caballus

race horse and Equus caballus both are nouns.

Word	Noun	Adjective	Verb	Adverb
race horse	Yes	No	No	No
Equus caballus	Yes	No	No	No

As nouns, Equus caballus is a hypernym of race horse; that is, Equus caballus is a word with a broader meaning than race horse:

race horse: a horse bred for racing
Equus caballus: solid-hoofed herbivorous quadruped domesticated since prehistoric times

Other hypernyms of race horse include horse.

race horse (noun)	Equus caballus (noun)
a horse bred for racing	solid-hoofed herbivorous quadruped domesticated since prehistoric times