FORMATION OF PLURALS IN WORDS OF FOREIGN ORIGIN
Reading edition
Plurals of nouns taken into English from other languages sometimes follow the laws of inflexion of those languages. But often, in non-technical works, additional forms are used, constructed after the English manner. Print as below, in cases where the author does not object. In scientific works the scientific method must of course prevail:
SING. addendum PL. addenda[26]
alkali alkalis
alumnus alumni
amanuensis amanuenses
analysis analyses
animalculum animalcula
antithesis antitheses
apex apices
appendix appendices
arcanum arcana
automaton automata
axis axes
bandit banditti
basis bases
beau beaux
bronchus bronchi
calculus calculi
calix calices
chrysalis chrysalises
coagulum coagula
corrigendum corrigenda{26}
cortex cortices
crisis crises
criterion criteria
datum data
desideratum desiderata
dilettante dilettanti
effluvium effluvia
elenchus elenchi
ellipsis ellipses
ephemera ephemerae
epithalamium epithalamia
equinox equinoxes
erratum errata
focus focuses (fam.)
formula formulae
fungus fungi
genius geniuses[27]
(meaning a person or persons of genius)
genus genera
helix helices
hypothesis hypotheses
ignis fatuus ignes fatui
index indexes[28]
iris irises
lamina laminae
larva larvae
lemma lemmas[29]
libretto libretti
matrix matrices
maximum maxima
medium mediums (fam.)
memorandum memorandums[30]
(meaning a written note or notes)
metamorphosis metamorphoses
miasma miasmata
minimum minima
nebula nebulae
nucleus nuclei
oasis oases
papilla papillae
parenthesis parentheses
parhelion parhelia
phenomenon phenomena
radius radii
radix radices
sanatorium sanatoria
scholium scholia
spectrum spectra
speculum specula
stamen stamens
stimulus stimuli
stratum strata
synopsis synopses
terminus termini
thesis theses
virtuoso virtuosi
volsella volsellae
vortex vortexes (fam.)