glacial epoch vs glacial period

glacial epoch and glacial period both are nouns.

Word	Noun	Adjective	Verb	Adverb
glacial epoch	Yes	No	No	No
glacial period	Yes	No	No	No

As nouns, glacial epoch and glacial period are synonyms defined as:

glacial epoch and glacial period: any period of time during which glaciers covered a large part of the earth's surface

Other synonyms of glacial epoch include ice age.

glacial epoch (noun)	glacial period (noun)
any period of time during which glaciers covered a large part of the earth's surface	any period of time during which glaciers covered a large part of the earth's surface