anestrus vs anestrum

anestrus and anestrum both are nouns.

Word	Noun	Adjective	Verb	Adverb
anestrus	Yes	No	No	No
anestrum	Yes	No	No	No

As nouns, anestrus and anestrum are synonyms defined as:

anestrus and anestrum: applies to nonhuman mammals: a state or interval of sexual inactivity between two periods of estrus

Other synonyms of anestrus include anoestrum, anoestrus.

anestrus (noun)	anestrum (noun)
applies to nonhuman mammals: a state or interval of sexual inactivity between two periods of estrus	applies to nonhuman mammals: a state or interval of sexual inactivity between two periods of estrus