yearling vs eutherian mammal

yearling and eutherian mammal both are nouns.

Word	Noun	Adjective	Verb	Adverb
yearling	Yes	No	No	No
eutherian mammal	Yes	No	No	No

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

yearling: an animal in its second year
eutherian mammal: mammals having a placenta; all mammals except monotremes and marsupials

Other hypernyms of yearling include eutherian, placental, placental mammal.

yearling (noun)	eutherian mammal (noun)
an animal in its second year	mammals having a placenta; all mammals except monotremes and marsupials
a racehorse considered one year old until the second Jan. 1 following its birth
a young child who is just beginning to walk