1. In & At

A) We use IN when we see a place as an area; we use AT when we see a place as a point.

i) I arrived AT New Delhi Station at 7.30. (place as a point)
ii) I’ll wait AT the far end of the room.
iii) We stayed IN Mumbai for five days. (here the city Mumbai means an area)
iv) My train stopped AT Mumbai on the way to Delhi. (place as a point; Mumbai = Mumbai Railway Station)
v) How long are you going to live IN this village? (place as an area)

NOTE: We use AT to talk about an event where there is a group of people and places we see them as a place of activity; e.g.

a) We last met AT the conference IN Delhi. (CONFERENCE = an event where there is a group of people. DELHI = a place as an area)
b) She always did well at school.
c) Buy me some biscuits AT baker’s. (BAKER’S means a shop that a baker runs.)

INCORRECT:  Did you see Sarla in the party?
CORRECT: Did you see Sarla AT the party?

INCORRECT:  There weren’t many people in the meeting.
CORRECT: There weren’t many people AT the meeting.

B) Workplaces when we see them as a physical location, we use IN (not AT). But if the workplace is a farm we use ON (not IN); e.g.

INCORRECT:  I work at a factory.
CORRECT: I work in a factory.

INCORRECT:  We sell garments at our shop.
CORRECT: We sell garments in our shop.

INCORRECT:  I want to work in a farm.
CORRECT: I want to work on a farm.

C) Before the names of streets we use IN and before a house-number we use AT; e.g.

i) He lives in Jawahar Street.
ii) He lives AT 45 Jawahar Street.

2. On

A) For a position touching a surface; things we think of as a line such as a road, a river; sea or lake we use ON; e.g.

i) Put your bag on the floor. (position touching a surface)
ii) I have my house on a river. (river thought as a line)
iii) The train is going to arrive on platform two. (platform thought as a line)

B) When we talk about a floor in a building we use ON; e.g.

INCORRECT: She lives at the 3rd floor.
CORRECT: She lives on the 3rd floor.

For more chapters/topics on English Grammar read the following book authored by me.

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For English Practice Sets on various topics read the following book authored by me.

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