spirilla vs spirillum

spirilla and spirillum both are nouns.

Word	Noun	Adjective	Verb	Adverb
spirilla	Yes	No	No	No
spirillum	Yes	No	No	No

As nouns, spirilla and spirillum are synonyms defined as:

spirilla and spirillum: any flagellated aerobic bacteria having a spirally twisted rodlike form

spirilla (noun)	spirillum (noun)
any flagellated aerobic bacteria having a spirally twisted rodlike form	any flagellated aerobic bacteria having a spirally twisted rodlike form
	spirally twisted elongate rodlike bacteria usually living in stagnant water