Some more examples of the most common irregular forms:
Singular Plural Comments um/on bacterium medium datum criterion phenomenon bacteria media data criteria phenomena 'Medium' has more than one meaning. As a person who claims to communicate with the dead, the plural is 'mediums'. As a method of expressing something, the plural is 'mediums/media'. is axis analysis crisis hypothesis thesis axes analyses crises hypotheses theses Note that 'es' is pronounced /i:z/ Not all words ending in 'is' follow this Latin rule e.g. irises, pelvises. ix/ex matrix appendix index matrices appendices indices 'Appendix' has two meanings. As a part of the body, the plural is 'appendixes' but as a part of a book, report etc., the plural is appendices. us nucleus radius stimulus nuclei radii stimuli Exceptions include syllabuses, prospectuses, censuses and viruses. Status remains unchanged or it can be 'statuses'. Other words can end in either 'es' or 'i'. e.g 'terminuses'/'termini'. add x to eau bureau tableau gateau bureaux tableaux gateaux You will sometimes see the ending 's' with these French words. a formula vertebra antenna vita formulae vertebrae antennae curriculum vitae The pronunciation of this ending varies: formulae /i:/ vertebrae /eɪ/ antennae /aɪ/ vitae /aɪ/ 'Antenna' has two meanings, each with a different plural form. Antennae are found on insects and crustaceans whilst antennas are found on radios and televisions. Some Italian plural nouns are rarely used in their original singular form. (graffito) (spaghetto) (panino) (paparazzo) graffiti spaghetti panini paparazzi These plural nouns are almost always used with the singular form of a verb.
1. When talking collectively about methods of broadcasting news - radio, TV, newspapers etc. - the plural of 'medium' is always 'the media' and it is now considered acceptable to use the singular form of a verb, although some people prefer the plural.
The media is/are covering the election.
The media has/have been accused of invading people's privacy.
2. 'Datum' is rarely used and you are likely to hear 'data' with the singular form of a verb as well as the plural.
The data is/are considered unreliable.
Most compound nouns have one part which is the 'head'. This means the basic or most important part of the noun. The other part(s) describe or modify the main noun. The formation of the plural depends on these 'heads'.
Rule | Examples |
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When the head is at the end, it takes its usual plural form. The first word is often an adjective or a noun that acts as an adjective. |
policeman swimming pool taxi rank toothbrush round the world cruise
|
policemen swimming pools taxi ranks toothbrushes round the world cruises
|
When there is just one head and it is at the beginning, it takes its usual plural form.
|
court martial mother-in-law passerby |
courts martial mothers-in-law passersby |
When there are two heads and the first has an irregular plural form, both are usually pluralised.
|
manservant woman doctor |
menservants women doctors |
When there are two heads and the first has a regular plural form, usually, only the second is pluralised.
|
city-state nurse-practitioner |
city-states nurse-practitioners |
When there are three or more words and the head has an irregular form, only that word is pluralised.
|
man-about-town lady-in-waiting |
men-about-town ladies-in-waiting |
For others with three or more words, either the first or the final head may be pluralised.
|
twelve-year-old head of state |
twelve-year-olds heads of states/heads of state |
With nouns that come directly from French and have a head at the beginning, both words are usually pluralised.
|
agent provocateur entente cordiale fait accompli |
agents provocateurs ententes cordiales faits accomplis |
With French nouns with the head at the end, either both words are pluralised or just the last one.
|
belle époque bon mot |
belle époques/belles époques bon mots/bons mots |
When French nouns have more than two words, the first is usually pluralised. |
coup d'état tour de force |
coups d'état tours de force
An exception is 'tête-à-têtes'.
|
As you can see, particularly with some Latin forms, we do not always follow the rules. This would probably be too complicated because it is not only the Latin ending which has to be considered but what kind of noun it is.
So, although you may see these correct forms, in everyday conversation you may also hear a regular 's' ending e.g. stadiums, formulas, brother-in-laws.
If you are unsure about a word that does not appear here, check in a good dictionary.
See also subject/verb agreement and compound nouns.