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.) | ||