1) AT — point / exact position
Place
Use at for a specific point, address, or location seen as a point.
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at the door
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at the bus stop
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at home
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at school (as an activity)
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at 221B Baker Street
Focus: position, not inside space.
Time
Use at for exact times and fixed moments.
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at 7:30
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at noon / at midnight
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at the moment
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at night (exception)
2) ON — surface / line / day
Place
Use on for surfaces or things touching a line or surface.
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on the table
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on the wall
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on the floor
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on the coast
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on the road
Contact with a surface is the key idea.
Time
Use on for days and dates.
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on Monday
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on July 4th
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on my birthday
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on the weekend (US; UK also at the weekend)
3) IN — enclosed space / longer period
Place
Use in for enclosed or defined areas.
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in the room
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in the box
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in the city
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in Brazil
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in the car (exception vs on the bus)
Focus: inside boundaries.
Time
Use in for longer periods.
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in 2026
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in March
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in the morning
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in the 21st century
Also for time until something happens:
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I’ll be back in two hours.
4) Common contrasts (very important)
Place
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at the cinema → location/activity
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in the cinema → inside the building
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on the bus → public transport
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in the car → private vehicle
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at school → studying/working
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in school → inside the building (less common)
Time
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at night ❌ in the night (general)
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in the night → specific night (storytelling)
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on time → punctual
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in time → early enough
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at the end → final point
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in the end → eventual result
5) Quick decision rule
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AT → exact point
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ON → surface or day
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IN → enclosed space or long period