yearling vs race horse

yearling and race horse both are nouns.

Word	Noun	Adjective	Verb	Adverb
yearling	Yes	No	No	No
race horse	Yes	No	No	No

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

yearling: a racehorse considered one year old until the second Jan. 1 following its birth
race horse: a horse bred for racing

Other hypernyms of yearling include bangtail, racehorse.

yearling (noun)	race horse (noun)
an animal in its second year	a horse bred for racing
a racehorse considered one year old until the second Jan. 1 following its birth
a young child who is just beginning to walk