A or an? How to choose
Short answer: Use a or an before one thing. Choose by the first sound of the next word, not the first letter. Use a before a consonant sound (a dog, a big egg) and an before a vowel sound (an apple, an hour). Look at the word right after a or an.
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At a glance
| Next word starts with | Use | Examples |
|---|---|---|
| a consonant sound | a | a cat, a book, a big apple |
| a vowel sound | an | an egg, an orange, an old hat |
| a silent h | an | an hour, an honest girl |
| a “you” sound | a | a uniform, a university |
In short
- a and an mean one.
- Listen to the first sound of the next word.
- a + consonant sound, an + vowel sound.
What is the rule for “A or An”?
The rule
Use a or an before one thing.
How it looks
a + a consonant sound: a dog, a cat, a ball. an + a vowel sound: an apple, an egg, an elephant.
What it means
a and an both mean one.
When to use it
Use them for one thing when we do not say which one.
How it works
- a and an both mean one. Use them only with one thing you can count.
- Say the next word out loud and listen to its first sound. Egg starts with a vowel sound, so an egg.
- Look at the very next word. The sound of that word decides: a big egg, but an old egg.
- With plural nouns and with nouns you cannot count, do not use a or an: cats, water.
Examples of “A or An”
- I have a cat.
cat starts with a /k/ sound: a cat. - She has an apple.
apple starts with a vowel sound: an apple. - It is a big egg.
Look at the word right after a: big starts with /b/, so a big egg. - Look, an umbrella!
umbrella starts with a vowel sound: an umbrella. - He eats an orange every day.
orange starts with a vowel sound: an orange. - She is an honest girl.
The h in honest is silent, so the word starts with a vowel sound: an honest girl. - It is a university.
university starts with a “you” sound, which is a consonant sound: a university. - I need a pen and an eraser.
pen starts with /p/: a pen. eraser starts with a vowel sound: an eraser.
Common mistakes with “A or An”
I have cat.→ I have a cat.
One cat needs a word before it: a cat.a apple→ an apple
apple starts with a vowel sound, so an.an big egg→ a big egg
Look at the next word: big starts with /b/.She is a engineer.→ She is an engineer.
engineer starts with a vowel sound, so we use an.I want an cake.→ I want a cake.
cake starts with /k/, a consonant sound, so we use a.
Exceptions: watch out
- an hour
The h is silent. We say "our", so an hour. - a uniform, a unicorn
u can sound like "you". That is a consonant sound, so a.
A or the? Which one do I use?
a and an introduce something new or something not special. the points to one particular thing that you and the listener both know.
| Use | Example | Why |
|---|---|---|
| a / an | I saw a dog. | any dog, the first time you mention it |
| the | The dog was big. | the dog we just talked about |
| the | Please open the window. | we both know which window |
See also: A or The?
Check yourself
- Fill the gap: “I have ___ apple.”
Show the answer
an apple starts with a vowel sound.
- Fill the gap: “She is ___ university student.”
Show the answer
a university starts with a “you” sound, a consonant sound.
- Fill the gap: “We waited for ___ hour.”
Show the answer
an The h in hour is silent, so the word starts with a vowel sound.
How to practice “A or An”
The interactive version adds step-by-step help, spoken instructions and a quick check. One rule card, one sound lesson and the first lesson of every stone are free to try; the rest is part of Full Access. See Full Access.
- Practice lesson: a or an?
Questions
Is it about the letter or the sound?
It is about the sound. Hour starts with a silent h, so it begins with a vowel sound and takes an. University starts with the letter u but sounds like “you”, so it takes a.
Do I use a or an with plural words?
No. a and an mean one. For more than one, use the plural without a: two apples, some eggs.
What about letters and numbers, like “an MBA” or “a 7”?
Say the first sound out loud. M is said “em”, so we say an MBA. Seven starts with /s/, so we say a seven.
More Grammar Foundations rules
- Naming words: nouns: A noun is a naming word. It names a person, an animal, a place or a thing.
- One and many: plural -s: For more than one thing, add -s: one cat, two cats.
- Plurals: -es, -ies and special nouns: Most nouns add -s. Some add -es or -ies, and some change a lot.
- this, that, these, those: Use this and these for things near you. Use that and those for things far away.
- I am, you are, it is: Use am with I, are with you and is with it.
- he, she, it, we, they + is / are: A pronoun takes the place of a name. Use is with he, she and it. Use are with we, you and they.
Used in these writing topics
Part of the 📘 Grammar tool. Level G1: Grammar Foundations. Đọc bằng tiếng Việt.
Written for English learners by the English for Fun team. How we write our lessons · Last updated 2026-11-05.
Reviewed by Chinh Q. Hoang, PhD, founder, English for Fun · 2026-10-30