Latin Plural Endings

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Pluralization of Latin-based nouns is a complicated field. Preference for Latin or English plural endings is inconsistent in similarly constructed words, as is the presence of alternative forms at all.

Here’s a guide to plural forms for Latin words, identifying, for more than a hundred nouns of Latin origin and a few similarly constructed terms from other languages, which ending among two or three alternatives is preferred for particular words or in which contexts various alternative forms are employed. When two or more alternatives are listed, the first is the more (or most) common.

Words ending in a, plural -s or -ae

alga: algae or algas
antenna: antennas or antennae (only antennae is correct for the sensory organs on animals; antennas in more common in other contexts)
formula: formulas or formulae
larva: larvae or larvas
nebula: nebulae or nebulas: the former ending is employed in astronomy, and the latter applies in medical contexts
vertebra: vertebrae or vertebras (vertebrae is sometimes incorrectly used to refer to a single vertebra)

Words ending in ex, plural -exes or -ices

apex: apexes or apices
index: indexes or indices
vortex: vortices or vortexes

Words ending in eau, plural -eaus or -eaux

bureau: bureaus or bureaux (the latter form is rare for this word and the other two in this category)
château: châteaus or châteaux
plateau: plateaus or plateaux

Words ending in ion, plural -ia

criterion: criteria
ganglion: ganglia or ganglions

Words ending in is, plural -es

analysis: analyses
axis: axes
basis: bases
crisis: crises
diagnosis: diagnoses
ellipsis: ellipses
hypothesis: hypotheses
oasis: oases
paralysis: paralyses
parenthesis: parentheses
synopsis: synopses
synthesis: syntheses
thesis: theses

Words ending in ix

appendix: appendixes or appendices
matrix: matrices or matrixes

Words ending in o, plural -os or -i

graffito: graffiti (the plural form is almost invariable used in place of the singular form)
libretto: librettos or libretti
virtuoso: virtuosos or virtuosi

Words ending in o, plural -os or -oes

armadillo: armadillos
avocado: avocados or avocadoes
banjo: banjos or banjoes
bistro: bistros
calypso: calypsos or calypsoes (the former spelling pertains to either the flower or the music style, and the latter form applies only to the music form)
cargo: cargoes or cargos
casino: casinos
contralto: contraltos
dingo: dingoes
domino: dominoes or dominos
dynamo: dynamos
echo: echoes or echos
ego: egos
embargo: embargoes
flamingo: flamingos or flamingoes
folio: folios
grotto: grottoes or grottos
hero: heroes
hippo: hippos
innuendo: innuendos or innuendoes
lasso: lassos or lassoes
mango: mangoes or mangos
motto: mottoes
paparazzo: paparazzi
pistachio: pistachios
portfolio: portfolios
potato: potatoes
radio: radios
ratio: ratios
rhino: rhinos or rhino
stiletto: stilettos or stilettoes
studio: studios
tornado: tornadoes or tornados
torpedo: torpedoes
veto: vetoes
volcano: volcanoes or volcanos
weirdo: weirdos

Words ending in oo, plural -oos

cockatoo: cockatoos
kangaroo: kangaroos
zoo: zoos

Words ending in um, plural -a or -ums

addendum: addenda or addendums
agendum: agenda or agendums (agenda is almost invariably used in place of the singular form, and agendums is rare)
aquarium: aquariums or aquaria
atrium: atria or atriums
bacterium: bacteria
candelabrum: candelabra or candelabrums
corrigendum: corrigenda
curriculum: curricula or curriculums
datum: data or datums (data is often used as a mass noun, taking a singular verb and being substituted by a singular pronoun)
erratum: errata
gymnasium: gymnasiums or gymnasia
maximum: maxima or maximums
medium: mediums or media (media is the correct alternative to refer to forms of expression or information or in biological contexts)
memorandum: memorandums or memoranda
millennium: millennia or millenniums
minimum: minima or minimums
moratorium: moratoriums or moratoria
podium: podiums or podia
referendum: referenda or referendums
spectrum: spectra or spectrums
stratum: strata
symposium: symposiums or symposia

Words ending in us, plural -uses or -i

alumnus/alumna: alumni or alumnae (alumnus refers to a man and alumna to a woman, alumni pertains to men or to men and women and alumnae to women; alumni is often employed in the singular, and alum/alums are used informally as gender-neutral singular and plural forms)
bacillus: bacilli
cactus: cacti or cactuses
focus: foci or focuses
fungus: fungi or funguses
hippopotamus: hippopotamuses or hippopotami
locus: loci
narcissus: narcissi or narcissuses or narcissus
platypus: platypuses or platypi
radius: radii or radiuses
stimulus: stimuli
syllabus: syllabi or syllabuses
terminus: termini or terminuses

Words ending in on, plural -a or -ons

automaton: automotons or automata
phenomenon: phenomena or phenomenons


cherub: cherubim or cherubs (the former alternative applies to angels and the latter pertains to depictions of winged children or to cherubic-looking people)
rhinoceros: rhinoceroses or rhinoceros or rhinoceri
seraph: seraphim or seraphs

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12 thoughts on “Latin Plural Endings”

  1. This list is a keeper. I like that the more commonly used version is listed first. (Though in many cases, I prefer to use the Latin, or French, or other foreign language version, regardless.) Thanks!

  2. “We speak of referendums, not referenda, on the advice of the editors of the Oxford English Dictionary: ‘Referendum is logically preferable as a plural form meaning ballots on one issue (as a Latin gerund referendum has no plural). The Latin plural gerundive referenda, meaning “things to be referred”, necessarily connotes a plurality of issues.'”

    From page 1 of Butler, D., & Ranney, A. (1994). Referendums around the world: The growing use of direct democracy. American Enterprise Institute.

  3. Mark, this is a very nice, very useful article. I am also pleased that you tackled a lot of technical words from engineering, physics, and mathematics: e.g.
    minima, maxima, spectra, automata, phenomena, radii, strata (actually geology), vertices, vortices, indices, axes, formulas (only British-types stick with formulae), and so forth.
    “Media” is used in physics (especially in wave propagation), mechanical engineering, electrical engineering, chemical engineering, etc. Example sentence: “Sound and light propagate at different speeds in different media,” where “media” refer to air, water and other liquids, vacuum, glass, crystals, metals, rock strata, ceramics, and so forth.
    Mark, your Big Winner is this one: “antenna: antennas or antennae (only antennae is correct for the sensory organs on animals; antennas in more common in other contexts)”.
    “Antennas” is used almost universally in electrical engineering and physics. See the textbook ANTENNAS, published by Dr. John D. Kraus in 1950, and its footnote on page one that says “antennas” is for technical uses, but “antennae” is used in zoology, especially concerning insects, crustaceans, scorpions, etc. ANTENNAS was the title of the textbook on the subject that my E.E. class used in Spring 1977.

  4. analyses, apices, axes, bases, ellipses, foci, hypotheses, indices, matrices, optima, parentheses, radii, separatices, spectra, syntheses, and vertices are all used in mathematics.

  5. Some words left out in Mark’s article:
    optimum, optima (and optimums)
    radix and radices (and radixes)
    separatrix and separatices
    I really can’t think of many because Mark made a nearly clean sweep!

  6. Nouns in German have a complicated and baffling system of making plurals, especially in the native German words from long ago. However, Mark’s list reminded me of several modern German words, and especially loanwords from English and other languages where they use “s” or “es” to form the plurals, just like in English, French, or Spanish:

    Radios, Radars, Computers, Autos (automobiles), Taxis, Hotels, Visas, Doktors, Professors, Transistors, Whiskeys, Yankees, Telefons (also Fernsprechers, using German roots), Televisions, and so forth. (Fernsehgerat, using German roots, means television or television set or TV set.)
    “Whiskey” is the only German word that I have found (in dictionaries) that begins with “Wh”. Of course, “Whiskey” is a loanword from Scottish and English. German words that begin with “Th” are also very rare.

  7. I agree that this is a very useful list. My only quibble is the title of the article, which suggests that all words in the list are derived from Latin. If this were the case, we wouldn’t see kangaroo and dingo (Australian), flamingo (Iberian), calypso (Greek), bistro (French), cockatoo (Indonesian), mango (Malayalam), paparazzo (Italian), or avocado (Nahuatl).

  8. @Andy Knoedler:
    That is a very nice and interesting observation that you made.
    You are a man of many words and languages!

  9. There are some words in the list, such as “armadillo” and “potato”, that probably came from Spanish or Native American languages.
    “Potatoes” contrasts strongly with its German and Russian equivalents: “Kartoffeln” and “Kartoshka”. I only know the latter because of my Russian friend, years ago, who loved to cook and eat potatoes.
    Potato plants came from the Inca area of South America. They were brought back to Spain by Spanish conquistadors and explorers, and then they spread to the famous “potato” countries of Germany, Poland, Russia, Ukraine, and Ireland. So, is “potato” a South American word or a Spanish one?

    There is the noted Mt. Palomar in Southern California. Some sources say that this is a Native American word, but others say that the Americans got the word from the Spanish. The word “Palomar” looks like it came from the word “paloma”, which the Spanish word for “pigeon” or “dove”. The area around Mt. Palomar was known for being inhabited by a lot of pigeons or doves.
    This is a puzzle and an enigma to me.

  10. All the checking of word origins can be credited to the Online Etymology Dictionary, which is worth its weight (if truly it has any at all) in gold. It tells us that “armadillo” is 100% Spanish, while “potato” was originally a Carib word taken up and distributed by the Spanish.

    Another useful website, Wikipedia, informs us that Palomar does indeed come from “pigeon” or “pigeon roost,” just as you surmised.

  11. Criterion should no be in here as it is Greek (or remove the word ‘Latin’ from the title). I see several others that should not be here, for example ‘paparazzo’ is Italian.

    Some of these I have never come across before, such as ‘matrixes’, ‘algas’ or ‘vortexes’.

  12. Bureau is French borrowed word, not Latin, like is château and plateau. I don’t understand how is it in a “Latin nouns” list!
    If they have “x” it’s because the plural of “eau” ending nouns make s “eaux” in French. Bureau for instance, in French, has a Greek root, not at all a Latin root.

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