Irregular Plural Nouns | Introduction to Writing – Skowronek (2024)

Irregular plurals, unlike regular plurals,don’t necessarily follow any particular pattern—instead, they follow a lot ofdifferent patterns. Because of this, irregular plurals require a lot of memorization; you need to remember which nouns belong to which type of pluralization.Mastering irregularsuses a different regionof yourbrain than regular pluralization:it’s an entirely different skill set than regular pluralization. So don’t get too frustrated if you can’t remember the correct plural. If you’re ever in doubt, the dictionary is there for you.

No Change (Base Plurals)

The first kind of irregular plural we’ll talk about is the no-change or base plural. In these words, thesingular noun has the exact same form as the plural. Most no-change plurals are types of animals:

• sheep
• fish
• deer
• moose

Mid-Word Vowel Change

In a few words, the mid-word vowels are changed to form the plural. This videolists all seven of these words and their plurals.

Note: The plural for a computer mouse (as opposed to the fuzzy animal) can either be mice or mouses. Some people prefermouses as it creates some differentiation between the two words.

Plural –en

And last we haveplural –en. In these words –en is used as the plural ending instead of –s or-es.

• child→ children
• ox→ oxen
• brother→ brethren
• sister→ sistren

Note:Brethrenand sistrenareantiquated terms that you’re unlikely to run into in your life; however, since these are the only four words in English that use this plural, all four have been included above.

Borrowed Words –i, –en, –a, –es, –ae

The last category of irregular plurals is borrowed words. These words are native to other languages (e.g., Latin, Greek) and have retained the pluralization rules from their original tongue.

Singular –us; Plural –i

• cactus→ cacti
• fungus→ fungi
• syllabus→ syllabi

In informal speech, cactusesand fungusesare acceptable.Octopuses is preferred tooctopi, butoctopi is an accepted word.

Singular-a; Plural –ae

• formula→ formulae (sometimesformulas)
• vertebra→ vertebrae
• larva→ larvae

Singular –ix, –ex; Plural –ices, –es

• appendix→ appendices (sometimes appendixes)
• index→ indices

Singular –on,–um;Plural –a

• criterion → criteria
• bacterium → bacteria
• medium→ media

Singular –is; Plural –es

• analysis→ analyses
• crisis→ crises
• thesis→ theses