streptococci vs streptococcus

streptococci and streptococcus both are nouns.

Word	Noun	Adjective	Verb	Adverb
streptococci	Yes	No	No	No
streptococcus	Yes	No	No	No

As nouns, streptococci and streptococcus are synonyms defined as:

streptococci and streptococcus: spherical Gram-positive bacteria occurring in pairs or chains; cause e.g. scarlet fever and tonsillitis

Other synonyms of streptococci include strep.

streptococci (noun)	streptococcus (noun)
spherical Gram-positive bacteria occurring in pairs or chains; cause e.g. scarlet fever and tonsillitis	spherical Gram-positive bacteria occurring in pairs or chains; cause e.g. scarlet fever and tonsillitis