Use an before a word that sounds like it starts with a vowel, and a before a word that sounds like it starts with a consonant. Listen to the word, don't look at its first letter.
- A goes before a consonant sound: a dog, a university.
- An goes before a vowel sound: an apple, an hour.
A: before a consonant sound
A goes before words whose first sound is a consonant. Some of these start with a vowel letter, but you don't say a vowel.
A dog barked.
A university is a big place.
A unicorn is a horse with a horn.
A one-hour trip is quick.
University and unicorn start with a yoo sound, which is a consonant sound. One starts with a w sound, as in won.
An: before a vowel sound
An goes before words whose first sound is a vowel. Some of these start with a consonant letter, but the letter is silent.
An apple fell from the tree.
An umbrella saved the picnic.
An hour is sixty minutes.
An honest answer is best.
Hour and honest begin with a silent H, so the first sound you say is a vowel.
Easy way to tell them apart
Say the word out loud and listen to the very first sound.
- Your mouth opens with an ah, eh, ih, oh or uh sound: use an.
- Your lips or tongue do something first, like y, w, b or h: use a.
📌 Good to Know
The same rule works for letters and short forms, because you say their names aloud. MP3 starts with the sound em, a vowel sound, so it is an MP3. FBI starts with ef, so it is an FBI agent. UFO starts with yoo, so it is a UFO.
When a word could be said two ways, follow how you say it.
💡 The OddLingo Trick
Think of the n as a little bridge. Two vowel sounds next to each other, as in a apple, bump into each other, so English adds an n to help them glide: an apple. (That's a memory trick, not the full history.)
That little n also has a story in Apron / Napron, where it moved between a and the next word. And the silent H in Honest and Hour is why those two take an.
⚠️ Common Mistakes
Is it a vowel sound? Listen, don't look.
❌ an university
✅ a university
Is there a silent letter? Then listen again.
❌ a hour
✅ an hour
Is it a letter you say aloud? Say its name.
❌ a MP3
✅ an MP3
A vowel letter does not always mean an.
❌ an unicorn
✅ a unicorn
💬 In a Conversation
Mia: I saw a unicorn.
Leo: An unicorn?
Mia: A unicorn. It starts with a yoo sound.
Leo: I need an hour to think about that.
Mia: An hour. Good. Not a hour.