archaebacteria vs archaebacterium

archaebacteria and archaebacterium both are nouns.

Word	Noun	Adjective	Verb	Adverb
archaebacteria	Yes	No	No	No
archaebacterium	Yes	No	No	No

As nouns, archaebacteria and archaebacterium are synonyms defined as:

archaebacteria and archaebacterium: considered ancient life forms that evolved separately from bacteria and blue-green algae

Other synonyms of archaebacteria include archaeobacteria, archeobacteria.

archaebacteria (noun)	archaebacterium (noun)
considered ancient life forms that evolved separately from bacteria and blue-green algae	considered ancient life forms that evolved separately from bacteria and blue-green algae