rodent vs eutherian mammal

rodent and eutherian mammal both are nouns.

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

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

rodent: relatively small placental mammals having a single pair of constantly growing incisor teeth specialized for gnawing
eutherian mammal: mammals having a placenta; all mammals except monotremes and marsupials

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

rodent (noun)	eutherian mammal (noun)
relatively small placental mammals having a single pair of constantly growing incisor teeth specialized for gnawing	mammals having a placenta; all mammals except monotremes and marsupials