1. Using a, an, the
A / An
Use a or an when you talk about something not specific or when mentioning it for the first time.
• a + words starting with a consonant sound
→ a book, a dog, a car
• an + words starting with a vowel sound (a, e, i, o, u)
→ an apple, an idea, an umbrella
Examples:
• I saw a dog. (not a specific dog)
• She bought an orange.
⸻
The
Use the when you talk about something specific or something that the listener already knows.
Use the for:
• Something both people know:
→ Close the door.
• Something mentioned before:
→ I saw a dog. The dog was big.
• Something unique in the world:
→ the sun, the Earth, the president
• Something made specific by a phrase:
→ the book on the table
Do NOT use the with:
• General ideas: I like music.
• Most names of people, cities, countries: Vietnam, John, Paris.
⸻
✅ 2. Using in, on, at
IN
Use in for large areas, enclosed spaces, or long periods of time.
Place:
• in a room
• in a city / country
• in the water
• in a car (closed space)
Time:
• in 2025
• in November
• in the morning / afternoon / evening
⸻
ON
Use on for surfaces, things touching a surface, or days.
Place:
• on the table
• on the wall
• on the beach
• on a bus / train / plane (you stand “on” the vehicle)
Time:
• on Monday
• on my birthday
• on January 1st
⸻
AT
Use at for specific points in place or time.
Place:
• at the bus stop
• at home
• at school
• at the door
• at 25 Nguyen Trai Street
Time:
• at 5:00
• at night
• at lunchtime
⸻
Quick Summary
A/An → not specific
The → specific
IN → large area / inside / months, years
ON → surface / days
AT → exact point / time
