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A vs. An: The Real Rule (It's About Sound, Not Spelling)
The a/an rule doesn't depend on the letter a word starts with, it depends on how it sounds.
Written by Bryan López, Profesor de inglés · Updated
Use a before a word that starts with a consonant sound, and an before a word that starts with a vowel sound. The most common mix-up is thinking it depends on the written letter: "a hotel" is correct because the H is pronounced, and "an hour" is also correct because the H in "hour" is silent.
Examples: the letter doesn't matter, the sound does
The real rule: sound, not spelling
The most common mistake is looking at whether the word starts with a, e, i, o, u on paper. The real rule is about pronunciation: use an when the starting sound is a vowel sound, no matter the letter. "An hour" and "a university" show exactly this: "hour" starts with a written vowel but sounds like a silent consonant, "university" starts with a written consonant but actually sounds like "yoo."
Exceptions with a silent h
When the H isn't pronounced, use an: an hour, an honest person, an honor. When the H is pronounced, use a: a hotel, a house, a happy day. There's no fixed list, you just have to know how each word sounds.
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Practice a vs. an with real audio
Interactive exercises, real pronunciation, and the full lesson taught in English.
Words that start with a vowel but sound like a consonant
University, European, one, uniform, and euro start with a written vowel, but their real sound starts like "y" or "w," which are consonant sounds: a university, a European trip, a one-way ticket, a uniform, a euro. That's why you use a, not an, even though the first letter is a vowel.
With acronyms and initialisms
With acronyms, it depends on how the first letter is pronounced, not what letter it is. If the letter sounds like a vowel (F, H, L, M, N, R, S, X), use an: an FBI agent, an MBA, an HR manager. If it sounds like a consonant, use a: a NASA mission (said as a word, "nasa"), a UFO (the U sounds like "yoo," a consonant sound).
Common mistakes learners make
In many languages, the equivalent of "a/an" depends on the noun's grammatical gender, not its starting sound, so it's natural to look at the written letter in English too. But English articles have no grammatical gender: the only question is how the word sounds out loud, not how it looks on paper.
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Frequently asked questions
What is the rule for using a or an in English?
Use a before a consonant sound and an before a vowel sound. The rule depends on pronunciation, not the written letter.
"A hotel" or "an hotel"?
"A hotel" is correct, because the H in "hotel" is actually pronounced (a consonant sound).
"A university" or "an university"?
"A university" is correct. Even though "university" starts with the vowel U, it actually sounds like "yoo-," which is a consonant sound.
When do you use "an" before a word with h?
When the H is silent, meaning it isn't pronounced: an hour, an honest person, an honor. If the H is pronounced, use a: a house, a hotel.
How do you use a/an with acronyms?
It depends on how the first letter is pronounced: an MBA, an FBI agent (F and M sound like vowels), but a NASA mission, a UFO (they sound like consonants).
"A" or "an" before a number?
It depends on how the number is pronounced: an 18-year-old ("eighteen" starts with a vowel sound), but a one-time offer ("one" sounds like "won," a consonant sound).
Practice a vs. an with real audio
Interactive exercises, real pronunciation, and the full lesson taught in English.