Use a before a consonant sound, and use an before a vowel sound—it’s about sound, not spelling. Source-1✅
The Correct Choice (In One Breath)
Think “What sound do I start with?” not “What letter do I start with?” Keep it spoken, not just written.
Table of Contents
Correct Form
A and an are the same indefinite article in two shapes. The choice is driven by the first sound you actually say, not the first letter you see on the page. Source-2✅
- Use “a” (consonant sound)
- a dog, a red apple, a European trip, a university course
- Use “an” (vowel sound)
- an ant, an umbrella, an hour, an 8-year-old
That’s why an hour is correct (the h is silent), and a university is correct (it starts with a “you” sound). Same letters, different first sound.
- Silent letters can flip the choice (hour, honest).
- Letter names matter for initialisms (MRI, FBI, URL).
- “U / Eu” can sound like “you” (university, European).
- “One / Once” starts with a “w” sound (one-off, once-in-a-lifetime).
Why The Mistake Happens
Most mix-ups happen when the first letter and the first sound don’t match. English spelling keeps a lot of history, borrowed patterns, and silent letters—so your eyes can be fooled even when your ears wouldn’t be. Source-3✅
Looks Like A Vowel, Sounds Like A Consonant
- a university (you-niversity)
- a European (you-ropean)
- a one-time deal (wun-time)
- a unicorn (you-nicorn)
Looks Like A Consonant, Sounds Like A Vowel
- an hour (silent h)
- an honest answer (silent h)
- an MRI (starts with “em”)
- an FBI agent (starts with “eff”)
Acronyms and initialisms are the sneakiest: the printed letters don’t matter as much as the spoken letter name. That’s how you get an MRI but a URL (because “U” is said like “you”).
Pronunciation and The Quiet N
In everyday speech, a is usually a relaxed /ə/, and an is a relaxed /ən/. That tiny n is there because it makes the sound transition smoother before a vowel sound. Source-4✅
This also explains why the “rule” can feel inconsistent on paper. Written English is fixed; spoken English is full of sound shortcuts, and a/an is one of the cleanest places where that shows up.
Word Origin and Word Parts
When you’re deciding between a and an, the most useful “word parts” are the letter groups that predict sound. A lot of confusion comes from a few repeating patterns—especially silent h and the “you” sound at the start of some u/eu words. Source-5✅
Patterns That Usually Predict “An”
- Silent h: an hour, an honest mistake, an heirloom
- Letter-name vowels: an MRI, an FBI briefing, an S-curve (because “S” starts with an “eh” sound)
- Numbers that begin with a vowel sound: an 8-minute wait, an 11-year span
Patterns That Usually Predict “A”
- “You” sound: a university, a unique idea, a European visitor
- “W” start: a one-off, a once-in-a-lifetime chance
- Some H words where the h is fully pronounced: a hotel, a hobby, a huge step
Word Family and Related Forms
A/an is the indefinite article: it points to a non-specific thing (“one of many”), not a particular known one. That meaning is stable even when the shape changes from a to an. Same job, different sound fit.
English has another well-known sound-based switch that feels similar: the is often pronounced differently depending on the next sound (a softer sound before consonants, a clearer one before vowels). It’s the same basic idea: speech flow matters.
- Allomorphs: a and an are two forms of one article, chosen by sound.
- Initialisms: choose by the first spoken letter name (MRI, FBI, URL).
- Borrowed words: spelling may look familiar, but pronunciation decides.
Common Misspellings Table
Below are the classic pairs where people swap a and an. Notice how the first sound (not the first letter) explains every “weird” case. Source-6✅
| Starter | Correct | Common Wrong | Why (Sound) | Example |
|---|---|---|---|---|
| hour | ✅ an hour | ❌ a hour | Silent h → starts with a vowel sound | I’ll be back in an hour. |
| honest | ✅ an honest answer | ❌ a honest answer | Silent h → vowel sound | That’s an honest answer. |
| university | ✅ a university | ❌ an university | Starts with “you” sound → consonant sound | She teaches at a university. |
| unique | ✅ a unique idea | ❌ an unique idea | “you” sound → consonant sound | It’s a unique idea. |
| European | ✅ a European city | ❌ an European city | “you” sound → consonant sound | They visited a European city. |
| one-time | ✅ a one-time offer | ❌ an one-time offer | Starts with “w” sound → consonant sound | It was a one-time offer. |
| MRI | ✅ an MRI | ❌ a MRI | “M” starts with “em” → vowel sound | They scheduled an MRI. |
| FBI | ✅ an FBI agent | ❌ a FBI agent | “F” starts with “ef” → vowel sound | They met an FBI agent. |
| URL | ✅ a URL | ❌ an URL | “U” starts with “you” → consonant sound | Please copy a URL. |
| 8-year-old | ✅ an 8-year-old | ❌ a 8-year-old | “eight” starts with a vowel sound | It’s an 8-year-old tradition. |
| 11-page | ✅ an 11-page report | ❌ a 11-page report | “eleven” starts with a vowel sound | They wrote an 11-page report. |
| hotel | ✅ a hotel | ❌ an hotel | h is usually pronounced in modern speech | They booked a hotel. |
If you ever see both forms in real writing for the same word, it’s usually because the pronunciation varies by speaker. That’s not “chaos,” it’s sound doing its thing.
- an university ❌ (should be a university)
- a hour ❌ (should be an hour)
- a MRI ❌ (should be an MRI)
- an one-time ❌ (should be a one-time)
FAQ
Frequently Asked Questions
Is It Based On Spelling Or Sound?
It’s based on sound. Use a before a consonant sound, and an before a vowel sound, even when the first letter suggests the opposite.
Why Is It “An Hour” But “A House”?
Hour starts with a vowel sound because the h is silent, so it takes an. House starts with a clear h sound, so it takes a.
Is It “A University” Or “An University”?
A university is the usual form because university begins with a “you” sound (a consonant sound), not a pure vowel sound.
How Do A And An Work With Abbreviations?
Go by how the abbreviation is said. If it starts with a vowel sound (“ef,” “em,” “ess”), use an. If it starts with a consonant sound (“you,” “dee,” “kay”), use a.
Is “An Historic” Wrong?
You may see an historic in some writing styles, but many speakers pronounce the h clearly and use a historic. The article follows the sound you actually use at the start.
What About Numbers Like 8 Or 11?
Use an when the number starts with a vowel sound in speech: an 8-year-old, an 11-page report. If the spoken form starts with a consonant sound, you’ll use a.