Irregular Plurals in English
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In a previous lesson, you saw the regular plurals of nouns in English. You also saw words that change how you pronounce and spell the ending.
In this lesson, we will see irregular plural forms.
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It is difficult to tell when a word has an irregular plural. The best way to learn them is to memorize the singular and plural forms together. Let’s look at the irregular plural of common words.
Review: Change in Pronunciation in Irregular Spelling
Sometimes there is a change in the pronunciation of the ending F or FE for some words, and you add -es to the end of those words. Other times, there is no change in pronunciation or spelling.
For nouns ending in F or FE, there are three ways to make the plural.
1. The F or FE changes to -ve before adding -s, so there is a change pronunciation of the ending.
knife - knives
life - lives
2. However, you just add -s to the end of some words, so the plural is completely regular.
chef - chefs
roof - roofs
3. Some nouns have both forms.
calf - calfs or calves
scarf - scarfs or scarves
For more examples of this type of plurals, see the lesson on regular plurals.
Irregular Plurals
Other irregular plurals have other changes in spelling, in pronunciation, or in both spelling and pronunciation.
No Change in the Plural
Words ending in -craft (meaning small boat or vessel)
one craft - many craft
one aircraft - many aircraft
one spacecraft - many spacecraft
Other words
one deer - many deer
one fish - many fish
one moose - many moose
one sheep - many sheep
one shrimp - many shrimp
one species - many species
one salmon - many salmon
one series - many series
Irregular Plurals with Word Change
Some words do not end in -s or -es in the plural form. The plural form
Irregular plurals
one child - many children
one foot - many feet
one goose - many geese
one man - many men
one ox - many oxen
one man - many men
one mouse - many mice
one tooth - many teeth
Note. Compound words ending in one of the above words keep the irregular plural.
one grandchild - many grandchildren
one schoolchild - many schoolchildren
one policeman - many policemen
one policewoman - many policewomen
Borrowed Words with Irregular Plurals
Many words in English come from other languages (e.g., Latin, Greek, French, Italian, Japanese). Many of these borrowed words kept the plural forms from the original language.
It does not matter what language an irregular plural came from. You just need to memorize it.
Singular -us becomes -i in the plural
The i is pronounced as the word “I.”
cactus - cacti
fungus - fungi
stimulus - stimuli
syllabus - syllabi
Note. Regular plurals for these words are also possible (“cactuses,” “funguses,” “syllabuses,” etc.), but the irregular plurals are much more common.
Singular -a becomes -ae
formula - formulae (pronounced as the “e” in “me”)
vertebra - vertebrae (pronounced as the “ey” in “hey”)
larva - larvae (pronounced as the “e” in “me”)
Note. Regular plurals are also possible for these words (formulas, vertebras, larvas), especially in spoken English.
Singular -ix or ex becomes -ices or -es
appendix - appendices
index - indices
vortex - vortices
Note. Regular plurals are also possible for these words (appendixes, indexes, vortexes), but the irregular plurals are more common in formal English.
Singular -on or -umbecomes a
bacterium - bacteria
criterion - criteria
medium - media
Singular -is becomes -es
The is and es are pronounced as “is" and “sees.”
analysis - analyses
basis - bases
crisis - crises
diagnosis - diagnoses
emphasis - emphases
parenthesis - parentheses
Other
graffito - graffiti (Italian)
kimono - kimono (Japanese)
plateau - plateaux (French)
Note. Borrowed words such as the above may end up changing to the regular (for example, one kimono, two kimonos; one plateau, two plateaus). Although “graffiti” is a plural in Italian, it is generally used as a singular word in English (as are “spaghetti” and “ravioli").
Practice
Practice 1. Complete this short exercises to assess what you have learned.
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