10.3.2. Tricky plurals
Some nouns do not form the plural by adding an -s to the end of the word.
Follow the list below:
| Singular | Plural |
|---|---|
| addendum | addenda |
| appendix | appendices (books) appendixes (anatomy) |
| bacterium | bacteria |
| bureau | bureaux |
| consortium | consortia |
| corrigendum | corrigenda |
| criterion | criteria |
| curriculum | curricula |
| embargo | embargoes |
| focus | foci (mathematics, science) focuses (other contexts) |
| formula | formulae (science) formulas (politics) |
| forum | forums (fora only in relation to ancient Rome) |
| genus | genera |
| index | indexes (books) indices (science, economics) |
| maximum | maxima (mathematics, science) maximums (other contexts) |
| medium | media (press, communications, IT) mediums (life sciences, art) |
| memorandum | memorandums or memoranda |
| minimum | minima (mathematics, science) minimums (other contexts) |
| moratorium | moratoriums or moratoria |
| papyrus | papyri or papyruses |
| phenomenon | phenomena |
| plus | pluses |
| premium | premiums |
| referendum | referendums or referenda |
| spectrum | spectra (science) spectrums (politics) |
| symposium | symposiums or symposia |
| vortex | vortices |