Collective Nouns

Collective nouns may take either singular or plural verbs, depending on whether the word refers to the group as a unit or to its members as individuals. In American English, most nouns naming a group regarded as a unit are treated as.

• Fifty percent of my time is spent on administration.
• Fifty percent of all physicians do not exercise regularly.
• The audience was enthralled. 
• This gathering is becoming noisy.
• At noon today, the jury delivers its verdict.

For a unit of measure, use a singular verb. 

• Five milliliters was injected.
• Two weeks of symptoms is common. 

Latin and Greek vs. English

There is a trend toward using English plurals rather than the traditional Latin or Greek. However, in most cases the latest edition of Merriam-Webster’s Collegiate Dictionary or Dorland’s or Stedman’s medical dictionary should be followed. Consistency within a manuscript is key.

SINGULAR	PREFERRED PLURAL
alga	algae
amoeba	amoebas
appendix	appendixes or appendices (consult dictionary for usage)
cannula	cannulas
condyloma acuminatum	condylomata, accuminata (with two-word Latin plurals, both parts become plural.)
cranium	crania
fistula	fistulas
formula	formulas
genus	genera
index	indices or indexes (consult dictionary for usage)
maxilla	maxillas
orbit	orbits
rhytid	rhytids
sequela	sequelae
vertebra	vertebrae

Microorganisms

When referring to the common vernacular plural of a genus, use roman lowercase letters. Consult the latest edition of Dorland’s or Stedman’s medical dictionary. For organisms that do not have a common plural, add the word species or organisms to the genus name to indicate a plural use. 

GENUS	PLURAL NOUN FORM
Chlamydia	chlamydiae
Escherichia	Escherichia organisms
Mycobacterium	mycobacteria
Proteus	Proteus species
Pseudomonas	pseudomonads
Salmonella	salmonellae
Staphylococcus	staphylococci
Streptcoccus	streptococci

When Not to Use Plurals

Beware of “pluralizing” nouns that cannot stand on their own as plurals.

Serum samples (not “sera”)

Urine tests (not “urines”)

False Singulars

Some nouns, because they end in a “plural” form, are mistakenly taken to be plurals even though they should be treated as singular and take a singular verb (e.g., measles, mumps, mathematics, genetics).

Measles is a deadly disease in underdeveloped countries.

A few nouns are usually used in the plural form; however, the distinction between plural and singular should be retained when appropriate. 

PLURAL	SINGULAR
data	datum
criteria	criterion
media	medium (for a specific type, television is a good medium for disseminating important health news.)
phenomena	phenomenon