archaebacterium vs archaeobacteria

archaebacterium and archaeobacteria both are nouns.

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

As nouns, archaebacterium and archaeobacteria are synonyms defined as:

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

Other synonyms of archaebacterium include archaebacteria, archeobacteria.

archaebacterium (noun)	archaeobacteria (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