2025.10.05

How to Form Singular and Plural Nouns｜Regular and Irregular Patterns

Izumi

In English, when distinguishing between “one item” and “two or more items,” nouns themselves change their form.

By correctly understanding and applying these changes, I can accurately convey numerical information, which significantly improves the precision of my reading, writing, and conversation in English.

In this lesson, I will explain the basic rules of plural forms in English nouns, their exceptions, and how they are used in sentences.

Contents

1. Basics of Singular and Plural Nouns
- 1-1. The Fundamental Difference Between Singular and Plural
- 1-2. Main Patterns of Plural Formation
2. Specific Rules for Plural Forms
3. Summary

1. Basics of Singular and Plural Nouns

1-1. The Fundamental Difference Between Singular and Plural

Singular form: one item/person
→ a book, one apple
Plural form: two or more items/people
→ two books, five apples

English nouns have a singular form (for one) and a plural form (for two or more).

The basic rule is to add -s or -es to the end of the word, but depending on the final letter, the form may change, and some words have irregular plural forms.

1-2. Main Patterns of Plural Formation

Singular	Plural	Rule/Explanation
book	books	Most common nouns simply add -s to form the plural, regardless of whether the final letter is a vowel or consonant.
bus	buses	Nouns ending in -s, -sh, -ch, -x, -z take -es to make pronunciation smoother.
baby	babies	For words ending in consonant + y, change y to i and add -es. Note the spelling change.
toy	toys	For words ending in vowel + y, simply add -s. Compare with baby.
knife	knives	Many nouns ending in -f, -fe change to -ves. However, there are exceptions.
man	men	Irregular change: both spelling and pronunciation change, so they must be memorized.
sheep	sheep	“Invariant” nouns: singular and plural forms are the same. The meaning is determined by context.

Since there are many exceptions in plural formation, it is also important to memorize each word individually.

2. Specific Rules for Plural Forms

2-1. The Basic Rule: Adding “-s”

This is the most frequently used and fundamental rule.

dog → dogs
book → books

Be aware of pronunciation differences, such as cats (/s/) and dogs (/z/). Both are grammatically correct plural forms, but the sound differs.

2-2. Adding “-es” for Easier Pronunciation

Words ending in -s, -sh, -ch, -x, -z require -es, since simply adding -s makes pronunciation difficult.

bus → buses
box → boxes
watch → watches

2-3. Special Changes for Words Ending in -y

For consonant + y: change y to i and add -ies.
Examples: city → cities, baby → babies
For vowel + y: simply add -s.
Examples: boy → boys, toy → toys

Tip:

Look at the letter before y. If it is a consonant, change y to i. If it is a vowel, leave y unchanged.

2-4. Nouns Ending in -f / -fe (With Exceptions)

Some nouns ending in -f / -fe change to –ves.

knife → knives
leaf → leaves

However, there are exceptions:

roof → roofs
belief → beliefs

These are conventional forms, so it is more efficient to learn commonly used words first.

2-5. Irregular Plural Nouns

These words undergo major changes in both spelling and pronunciation, and must be memorized.

man → men
woman → women
child → children
tooth → teeth
foot → feet

Irregular plurals appear frequently in both conversation and writing, so I should become familiar with them early.

2-6. Invariant Nouns (Same in Singular and Plural)

Some nouns have the same form in both singular and plural, such as sheep, deer, fish.

One sheep is eating grass.
Ten sheep are eating grass.

In these cases, I must determine singular or plural based on numbers and verbs in the sentence.

3. Summary

In English, nouns change form depending on number.
The basic plural rule is to add -s.
Depending on the ending, changes such as -es / -ies / -ves are required.
For nouns ending in consonant + y, change y to i + -es. For vowel + y, simply add -s.
Irregular plurals must be memorized, starting with frequently used words.
Some nouns (sheep, fish, deer) have the same form in both singular and plural, so context is key.
When a number is present, the noun must be in plural form. (three cats)