What are Cardinal Numbers?
In English, Cardinal Numbers (1, 2, 3, etc.) express exact quantity — they answer the question "how many?" They are the most basic and frequently used numbers in English, appearing in counting, measurements, ages, prices, times, and more. Understanding how to spell and combine these numbers is essential for clarity in daily communication.
Cardinal Numbers Structure and Formula
Cardinal numbers function as determiners before a noun. The general structure follows a straightforward pattern:
Formula:
- Number (1) + Noun (singular countable) + V (singular)
- Number (>1) + Noun (plural countable) + V (plural)
Example: One child is playing. / Twenty children are playing.
How to Form Numbers 1–20 Options
The foundation of the counting system begins with the numbers 1 through 20. Many of these have unique names that must be memorized.
| Number | Word | Number | Word |
|---|---|---|---|
| 1 | one | 11 | eleven |
| 2 | two | 12 | twelve |
| 3 | three | 13 | thirteen |
| 4 | four | 14 | fourteen |
| 5 | five | 15 | fifteen |
| 6 | six | 16 | sixteen |
| 7 | seven | 17 | seventeen |
| 8 | eight | 18 | eighteen |
| 9 | nine | 19 | nineteen |
| 10 | ten | 20 | twenty |
💡 Tip:
- Numbers 13–19 almost all end in -teen (note the slight spelling shifts: thir-teen, fif-teen).
- 11 and 12 (eleven, twelve) are completely irregular and do not follow the "-teen" rule.
How to Form Tens and Compound Numbers (21–99)
Once you pass 20, the numbers follow a very strict, repeating compound pattern.
Tens: 20–100
The "tens" end in -ty:
| Number | Word | Number | Word |
|--------|------|--------|------|
| 20 | twenty | 60 | sixty |
| 30 | thirty | 70 | seventy |
| 40 | forty (Not fourty!) | 80 | eighty |
| 50 | fifty | 90 | ninety |
Compound Numbers (21–99)
To form numbers between the tens, you combine the ten word and the unit word. In written English, you must always use a hyphen (-) between them.
| Number | Word Structure | Output |
|---|---|---|
| 21 | twenty + one | twenty-one |
| 35 | thirty + five | thirty-five |
| 48 | forty + eight | forty-eight |
| 99 | ninety + nine | ninety-nine |
How to Identify Hundreds, Thousands, and Millions
When dealing with large amounts, the base words are hundred, thousand, million, and billion.
| Number | Word |
|---|---|
| 100 | one hundred |
| 200 | two hundred |
| 365 | three hundred and sixty-five |
| 1,000 | one thousand |
| 5,280 | five thousand two hundred and eighty |
| 1,000,000 | one million |
💡 Tip: Notice that words like hundred and thousand never take an "s" when they follow a specific number. You say "five hundred," never "five hundreds."
When to Use Cardinal Numbers with Nouns
Cardinal numbers are placed directly before the noun.
| Pattern | Example |
|---|---|
| Number (>1) + Noun (plural) | three books, twenty students |
| Number (1) + Noun (singular) | one apple, a cup (A/An can replace One) |
| One hundred vs. a hundred | Both are correct: a hundred cars / one hundred cars |
- I have two sisters and one brother. (S + V + O)
- The building has thirty-five floors.
Specific Situations
Telephone Numbers
Say each digit individually. For zero, say "oh" (UK) or "zero" (US).
0800 → "oh eight hundred"
Prices
State the whole currency amount, then the smaller units.
£4.99 → "four pounds ninety-nine"
$2.50 → "two dollars fifty"
Ages
Simply use the verb "to be" + the number. No "years old" is required in casual speech.
She is twenty-three.
Years
Split four-digit years into two pairs.
1990 → "nineteen ninety"
2024 → "twenty twenty-four"
Real-life Examples of Cardinal Numbers Usage
- There are seven days in a week and twelve months in a year.
- My phone number is zero seven nine three four (07934...).
- The ticket costs forty-five pounds.
- She moved to London twenty-three years ago.
Summary & Cheatsheet for Cardinal Numbers
| Range | Pattern | Example |
|---|---|---|
| 1–12 | Unique words | one, two… twelve |
| 13–19 | Root + -teen | thirteen, fifteen |
| 20–90 | Root + -ty | twenty, fifty |
| 21–99 | Tens-unit (hyphenated) | thirty-four |
| 100+ | Number + hundred/thousand + (and) | three hundred and twelve |
Frequently Asked Questions
Do I say "three hundred sixty-five" or "three hundred and sixty-five"?
Both are grammatically correct, though they differ by region. In British English, it is standard to include "and" after the word "hundred" (three hundred and sixty-five). In American English, the "and" is usually omitted (three hundred sixty-five).
Why shouldn't I say "I have twenty years"?
In English, age is viewed as a state of being rather than a possession. Therefore, you must use the verb "to be" rather than "to have". Let's use the formula: S + be + Cardinal Number: I am twenty or I am twenty years old.
How do I spell 40? Is it fourty or forty?
The correct spelling is forty, without the "u". While 4 is four and 14 is fourteen, the "u" disappears in the tens form!
Can "hundred" or "thousand" ever be plural?
Yes, but only when you are talking about an unspecific, large amount (not tied to an exact number), and you must follow it with "of". For example: Hundreds of people came to the concert. or It cost thousands of dollars. But if there is a specific number in front, never use an "s" (five hundred people).