The Weird World of Irregular Plurals
  • 3-minute read
  • 4th August 2016

The Weird World of Irregular Plurals

The English language is like an old friend with a habit of playing horrible pranks: no matter how much you enjoy its company, it’ll eventually surprise you with something unpleasant.

Like covering your desk in cling wrap. [Photo: Matt Reinbold/flickr]
Irregular plurals, for instance, are words that defy normal spelling rules, as if designed to catch people out! Luckily, there are some guidelines to help you spell them correctly.

What are Irregular Plurals?

Irregular plurals don’t follow the normal convention of adding an ‘-s’ when forming a plural (e.g. like how ‘plural’ becomes ‘plurals’). The most common examples are words that end in a consonant plus ‘-y’, where the ‘-y’ changes to ‘-ies’ when pluralised (e.g. ‘lady’ becomes ‘ladies’).

But there are lots of other irregular plurals. The following, for example…

Words Ending ‘-o’ or ‘-a’

Most words that end in ‘-o’ simply require adding an ‘-s’ to form the plural (e.g. ‘hippo’ → ‘hippos’), but some take ‘-oes’ instead, such as when ‘hero’ becomes ‘heroes’. Others include:

Singular

Plural

Potato

Potatoes

Echo

Echoes

Torpedo

Torpedoes

Similarly, words which end with ‘-a’ are sometimes spelled with ‘-ae’ when pluralised:

Singular

Plural

Formula

Formulae

Vertebra

Vertebrae

Antenna

Antennae

In some cases this is a matter of choice, however, as modern conventions may permit alternatives, such as when ‘antenna’ is pluralised as ‘antennas’.

Words Ending ‘-f’ or ‘-fe’

Words that end ‘-f’ or ‘-fe’ are usually spelled with a ‘-ves’ in plural form. For instance:

Singular

Plural

Knife

Knives

Elf

Elves

Life

Lives

One important exception is when a word ends ‘-ff’, in which case you simply add an ‘-s’ to make a plural (e.g. ‘quiff’ → ‘quiffs’).

Words Ending ‘-is’

Words ending ‘-is’ in the singular generally take ‘-es’ when pluralised. This includes:

Singular

Plural

Analysis

Analyses

Thesis

Theses

Diagnosis

Diagnoses

Words Ending ‘-ix’ or ‘-ex’

Terms that end either ‘-ix’ or ‘-ex’ are traditionally spelled with ‘-ices’ when pluralised:

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Singular

Plural

Index

Indices

Appendix

Appendices

Matrix

Matrices

However, in recent years, regular plural versions of these words have become more common. You may therefore see other spellings used, such as ‘indexes’ and ‘appendixes’.

Words Ending ‘-on’, ‘-um’ or ‘-us’

Additional word endings to look out for include ‘-on’ and ‘-um’, which are both often replaced with ‘-a’ in plurals (e.g. ‘medium’→ ‘media’), as well as ‘-us’, which changes to ‘-i’ (‘alumnus’ → ‘alumni’):

Singular

Plural

Phenomenon

Phenomena

Bacterium

Bacteria

Nucleus

Nuclei

Keeping You Guessing…

To increase the confusion, some words change even more when pluralised:

Singular

Plural

Child

Children

Tooth

Teeth

Mouse

Mice

There’s no real pattern here; often it’s the vowel sound that changes (e.g. ‘tooth’ and ‘teeth’), but this isn’t always the case (e.g. ‘child’ and ‘children’).

No Change Required!

Finally, some plurals are irregular because they don’t change at all when pluralised! A single ‘fish’, for instance, is spelled the same as when describing a ‘shoal of fish’. Other examples include ‘deer’, ‘offspring’ and ‘species’.

And don’t forget, if you struggle with spelling, getting your work proofread is a fantastic way of catching mistakes you might have missed.

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