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Spelling Tip: Latin and Greek Plurals

This spelling tip examines the various endings of plural words derived from Latin and Greek.

Nouns that originated from Latin and Greek are common in scientific and medical writing.

The preferred plural form of many of these words is the same as in the original language. But for other plurals, the usual English rules of adding "s" or "es" now apply. Some words are in transition, either form being commonly used.


Table 1 shows common traditional endings for Latin or Greek singular nouns and their corresponding plural endings.

Table 1.
Common Latin and Greek Noun Endings

Singular ending             Plural ending
-a -ae
-en -ina
-ex -ices
-is -es
-itis -itides
-ix -ices
-on -a
-um -a
-us -i

Table 2 presents singular and plural forms of selected nouns derived from Latin and Greek. English forms are shown in bold.

Some dictionaries indicate that the two plural forms—traditional and English—occur with equal frequency. However, the acceptability of an English plural form may differ by publication.

Caution: Read the dictionary entry carefully. Sometimes the English plural is used for only a narrow definition of the term.

Table 2.
Singular and Plural Nouns Derived From Latin and Greek

Singular form Plural form
alga algae or algas
analysis analyses
bacterium bacteria
basis bases
criterion criteria or criterions
datum data
focus foci or focuses
foramen foramina or foramens
formula formulae or formulas
fungus fungi or funguses
genus generaa
hypothesis hypotheses
index indices (math) or indexes
larva larvae or larvas
matrix matrices or matrixes
medium media
nephritis nephritides
nucleus nuclei or nucleuses
parenthesis parentheses
phenomenon phenomena
radius radii or radiuses
stimulus stimuli
stratum strata
synthesis syntheses
vertebra vertebrae or vertebras

aThe plural ending for this word is an exception to the rule (see Table 1).

Quick Tips: Latin and Greek Plurals

Speedy pencil: quick grammar tips
  1. Learn the traditional Latin and Greek plural endings (Table 1).

  2. Check your dictionary (standard, medical) for the preferred plural form.

  3. Above all, use the plural form consistently within your document.


Council of Science Editors, Style Manual Committee. Scientific Style and Format: The CSE Manual for Authors, Editors, and Publishers. 7th ed. Reston, VA: The Council; 2006

Merriam-Webster's Collegiate Dictionary. 11th ed. Springfield, MA: Merriam-Webster, Inc.; 2007.

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