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Numbers are the backbone of English communication, yet I’ve watched countless ESL students stumble over them. I once taught a class where a learner said “the twenty-one peoples” instead of “twenty-one people,” and another who confused “second” (ordinal) with “two” (cardinal) in a job interview. These aren’t small mistakes — numbers appear everywhere: dates, prices, rankings, measurements, phone numbers, scores. Get them right, and you sound fluent. Get them wrong, and people will remember it.
You’ll covers all the number types you need: cardinal numbers (how many), ordinal numbers (which position), fractions (parts of a whole), and decimals (precise measurements). You’ll learn the rules for when to write numbers as words versus numerals, and see real examples of how native speakers use them in context. By the end, you’ll be able to handle numbers with confidence in any conversation or document.
Key Takeaways
- Cardinal numbers (one, two, three) are for counting; ordinal numbers (first, second, third) show position in a sequence.
- Fractions use cardinals in the numerator and ordinals in the denominator: one-third, two-fifths, three-eighths.
- Decimals are read digit-by-digit: 3.14 is “three point one four,” not “three point fourteen.”
- Hyphenation rule: Use hyphens for numbers 21–99 (twenty-one, ninety-nine) but not for multiples of ten (twenty, thirty).
- Writing choice: Use words for numbers one to nine in formal writing; use numerals for 10 and above, except in special cases.
Understanding Numbers: Four Core Types
English uses four main categories of numbers, each serving a different purpose. Understanding when to use which type is essential.
Cardinal Numbers
Cardinal numbers answer the question “How many?” They are the numbers you use when counting objects, people, money, or anything with quantity. One, two, three, four — these are the first numbers children learn because they’re fundamental to everyday communication.
Example: “I have three cats and two dogs.” The words “three” and “two” are cardinals because they tell you the quantity of each animal.
Ordinal Numbers
Ordinal numbers answer the question “Which position?” They show the order or rank of something in a sequence. First, second, third — ordinals appear in dates, races, rankings, and lists.
Example: “She came in first place. He came in second. The third-place finisher was close behind.” Here, ordinals tell you the rank of each competitor.
Fractions
Fractions represent parts of a whole. In English, the numerator is a cardinal and the denominator is an ordinal, with one exception: the denominator “two” becomes “half” (one-half, not one-second).
Example: “The recipe calls for two-thirds of a cup of flour.” Here, “two-thirds” is the fraction.
Decimals
Decimals express non-whole numbers using a decimal point. They appear in prices, measurements, percentages, and scientific data. The key rule: read decimals digit by digit after the point.
Example: “The temperature is 23.5 degrees Celsius.” You say “twenty-three point five,” not “twenty-three and a half,” because it’s a decimal, not a fraction.
Cardinal Numbers: The Counting System
Cardinal numbers form the foundation of all other number types. Mastering them opens the door to everything else.
| 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 | 20 | Twenty |
| 7 | Seven | 30 | Thirty |
| 8 | Eight | 50 | Fifty |
| 9 | Nine | 100 | One hundred |
| 10 | Ten | 1,000 | One thousand |
Compound numbers (21–99) use hyphens: twenty-one, forty-five, ninety-nine. But multiples of ten don’t: twenty, thirty, forty.
Example uses of cardinal numbers:
- “I need to buy two dozen eggs for the recipe.”
- “She scored a perfect ten on her gymnastics routine.”
- “My phone number is 555-1234.”
- “The total cost came to one hundred and fifty dollars.”
- “There are 365 days in a year.”
Ordinal Numbers: Position and Sequence
Ordinal numbers describe the position of something in an ordered list. They’re used in dates, rankings, lists, and any context where order matters.
| Cardinal | Ordinal | Cardinal | Ordinal |
|---|---|---|---|
| 1 | First | 11 | Eleventh |
| 2 | Second | 12 | Twelfth |
| 3 | Third | 13 | Thirteenth |
| 4 | Fourth | 20 | Twentieth |
| 5 | Fifth | 21 | Twenty-first |
| 6 | Sixth | 22 | Twenty-second |
| 7 | Seventh | 50 | Fiftieth |
| 8 | Eighth | 100 | Hundredth |
| 9 | Ninth | 1,000 | Thousandth |
| 10 | Tenth | 1,000,000 | Millionth |
Note the irregular forms: five → fifth, eight → eighth, nine → ninth, twelve → twelfth. Most others follow a pattern: four → fourth, seven → seventh.
Real-world examples of ordinal numbers:
- “The first day of school is always exciting.”
- “She came in second place in the marathon.”
- “The third book in the series is my favourite.”
- “He was the fourth person to arrive at the party.”
- “The fifth floor of the building has the best view.”
- “We are celebrating our twenty-fifth wedding anniversary.”
Tip for dates: In English, dates use ordinals: “The fourth of July” or “July the fourth.” Both are correct, though Americans often say it the second way.
Fractions: Parts of a Whole
Fractions appear constantly in recipes, measurements, and everyday descriptions. The rule is simple: the top number is cardinal, the bottom is ordinal.
| Fraction | How You Say It | Context |
|---|---|---|
| 1/2 | One-half (or “half”) | “The recipe calls for one-half cup of sugar.” |
| 1/3 | One-third | “A third of the class was absent.” |
| 2/3 | Two-thirds | “Two-thirds of the students passed the exam.” |
| 1/4 | One-quarter (or “a quarter”) | “A quarter of the pie is left.” |
| 3/4 | Three-quarters | “The glass is three-quarters full.” |
| 1/5 | One-fifth | “One-fifth of the budget is allocated to marketing.” |
Example sentences with fractions:
- “Add half a cup of flour to the mixture.”
- “Three-quarters of the team voted in favour of the proposal.”
- “The project is one-third complete.”
- “A fifth of the annual revenue goes to research and development.”
Decimal Numbers: Precision and Measurement
Decimals are essential in science, finance, and any field requiring precision. The key is reading them correctly: digit by digit after the decimal point.
How to read decimals:
- 3.14 = “three point one four” (not “three point fourteen”)
- 0.5 = “zero point five” (or “point five”)
- 12.75 = “twelve point seven five”
- 100.001 = “one hundred point zero zero one”
Real-world examples of decimal numbers:
- “The price of the item is $3.99.”
- “The temperature is 23.5 degrees Celsius.”
- “The interest rate is 5.25 per cent.”
- “The weight of the object is 0.75 kilograms.”
- “The length of the room is 4.5 metres.”
- “Your batting average is 0.325 (read: ‘point three two five’).”
Decimal vs. Fraction: A decimal 0.5 is NOT the same as saying “zero and a half.” Say “zero point five” or “point five.” The word “point” signals you’re reading a decimal, not a fraction.
Common Mistakes
✗ Incorrect: “She came in the third place.”
✓ Correct: “She came in third place.” (or “She came in third.”)
Why: Ordinal numbers don’t need “the” in this context. You say “first place,” “second place,” not “the first place,” “the second place.”
✗ Incorrect: “The phone number is five-five-five, one two three four.”
✓ Correct: “The phone number is five-five-five, one-two-three-four.” (or individual digits read one at a time)
Why: Phone numbers are read digit by digit, and each digit is a cardinal number. When writing it out, you’d write 555-1234 or (555) 123-4.
✗ Incorrect: “Three-quarter of the pie is gone.”
✓ Correct: “Three-quarters of the pie is gone.” (or “Three-quarter of the pie is gone” if used as an adjective, e.g., “a three-quarter cup”)
Why: When fractions are nouns standing alone, they’re plural: quarters, fifths, eighths. When used as adjectives modifying a noun, the compound may be singular: three-quarter cup, one-third portion.
✗ Incorrect: “The decimal 3.14 is ‘three point fourteen.'”
✓ Correct: “The decimal 3.14 is ‘three point one four.'”
Why: Decimals are read digit by digit after the point. Pi is 3.14, said as “three point one four,” never “three point fourteen.”
Student: How do I say my phone number in English?
Teacher: Each digit is spoken individually. So 555-1234 becomes “five-five-five, one-two-three-four.”
Student: And if I want to say a fraction?
Teacher: Top number is cardinal, bottom is ordinal. One-third, two-fifths, three-eighths. Except one-half — we say “half” instead of “second.”
Student: What about 3.14?
Teacher: That’s a decimal, so “three point one four” — digit by digit. Not “three point fourteen.”
Quick Quiz: Test Your Number Skills
- Write 42 in words: ________
- The ordinal form of 9 is ________.
- How do you say 2/5? (a) two-five / (b) two-fifths / (c) two-fifth
- The decimal 5.03 is read as “five point ________”.
- In the phrase “_________ time’s the charm,” which number goes in the blank? (first / second / third)
Answers: 1. forty-two · 2. ninth · 3. two-fifths · 4. zero three (or “oh three”) · 5. third
Writing Numbers: Words vs. Numerals
Professional and formal writing requires consistency. Here are the standard rules:
When to Write Numbers as Words
- Numbers one to nine in formal or academic writing.
- Numbers at the beginning of a sentence (always spell them out).
- Approximate numbers (“about twenty people attended”).
- Formal documents like contracts or cheques.
Examples: “Three hundred employees attended the conference.” “She waited for five minutes.” “Between fifty and sixty countries participated.”
When to Write Numbers as Numerals
- Numbers 10 and above in most writing.
- All numbers in technical, scientific, or financial writing.
- Dates, times, measurements, and percentages.
- Phone numbers, addresses, and identification numbers.
Examples: “The cost was 150 euros.” “The temperature reached 35°C.” “The event is on 15 July 2024.” “Call 555-1234 for information.”
Related Articles
- ↑ Master Pillar: English Vocabulary
- ↑ Back to pillar: English Vocabulary (Topical)
Frequently Asked Questions
What are the basic cardinal numbers in English?
Cardinal numbers are the basic counting numbers: one, two, three, four, five, etc. They answer “how many?” Use them for quantities of any kind — people, objects, money, time.
How do I write compound numbers like 25 or 47?
Compound numbers between 21 and 99 use a hyphen: twenty-five, thirty-seven, forty-seven, ninety-nine. But multiples of ten stand alone: twenty, thirty, forty, fifty. Never hyphenate multiples of ten.
What’s the difference between a fraction and a decimal?
Fractions (1/2, 3/4, 2/5) show parts using a numerator and denominator and are said with ordinals: “one-half,” “three-quarters.” Decimals (0.5, 0.75, 0.4) use a decimal point and are read digit by digit: “zero point five,” “zero point seven five.”
How are ordinal numbers used in dates?
Dates use ordinals: “the fourth of July,” “July the fourth,” “the twenty-first of March.” In written form, you may see “July 4th,” where the “th” is the ordinal suffix. Both spoken forms are correct in English.
Do I use ordinal numbers for years?
No. Years are always cardinal numbers: “nineteen eighty-four,” “two thousand twenty-six,” “twenty twenty-five.” Never say “the twenty twenty-sixthth” — it’s just “twenty twenty-six.”
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