Use “an” before vowel SOUND
If the next word starts with a vowel sound (a, e, i, o, u sounds), use an.
Silent letters also matter.
- an apple, an umbrella
- an hour (h is silent → vowel sound)
- an MBA / an MLA (starts with “em” sound)
Common mistake: “a hour” ❌ (correct: an hour ✅)
Exam trick: If you can say “em / en / ef” while reading the first letter, usually it takes an (an M…, an N…, an F…).