How to Form Regular Plural Nouns
The most common way to form the plural of a noun in English is by adding -s to the end of the word. This rule applies to most nouns. For example:
book → books
car → cars
table → tables
dog → dogs
However, if the noun ends in -s, -ss, -sh, -ch, -x, or -z, the plural is formed by adding -es. For example:
bus → buses
glass → glasses
lunch → lunches
box → boxes
For nouns ending in -o, the plural is usually formed by adding -es. For example:
tomato → tomatoes
mosquito → mosquitoes
hero → heroes
echo → echoes
But there are exceptions where only -s is added:
piano → pianos
photo → photos
kilo → kilos
video → videos
For nouns that end in a consonant followed by -y, the -y is usually changed to -ies to form the plural. For example:
city → cities
baby → babies
story → stories
party → parties
If the noun ends in a vowel followed by -y, simply add -s:
boy → boys
day → days
key → keys
journey → journeys
For most words ending in -f or -fe, we change the -f to a -v and then add -es:
leaf → leaves
half → halves
wife → wives
life → lives
However, there are some exceptions where the -f doesn’t change and only -s is added:
roof → roofs
belief → beliefs
chef → chefs
cliff → cliffs
If the noun ends in -us, the plural ending is often -i:
cactus → cacti
focus → foci
alumnus → alumni
radius → radii
If the singular noun ends in -is, the plural ending is -es:
thesis → theses
crisis → crises
diagnosis → diagnoses
analysis → analyses
Irregular Plural Nouns
English has many nouns that don’t follow the regular pluralization rules. These irregular plurals must be memorized, as there are no specific rules to follow. Here are some common examples:
child → children
man → men
woman → women
person → people
foot → feet
tooth → teeth
mouse → mice
Some nouns retain their original form when pluralized. That is, the singular and plural form of the word are the same. For example:
sheep (one sheep, two sheep)
fish (one fish, two fish) – though fishes is also acceptable in certain contexts
series (one series, two series)
species (ones species, two species)
