yearling vs placental

yearling and placental both are nouns.

Word	Noun	Adjective	Verb	Adverb
yearling	Yes	No	No	No
placental	Yes	Yes	No	No

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

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

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

yearling (noun)	placental (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

yearling (adjective)	placental (adjective)
	pertaining to or having or occurring by means of a placenta