At

출처: English Grammar Today

At is a preposition. We use at to refer to time or place. We also use it to refer to activities.

At: time

We use at to talk about points in time, ages and some periods of time:

I was up at 6 am this morning. (a point in time)

At 12 noon, all the bells rang out. (a point during the day)

They all get dressed up at Halloween. (a point on the calendar)

Many children leave school at 16. (referring to a specific age)

At 20, I thought I knew everything.

We can use at to refer to some periods of time: at night, at that time, at the New Year:

They leave the front-door light on at night. (period of time)

At: place

We use at to describe a position or location seen as a point:

A fisherman waited near his nets at the side of the quay. (position as a point)

There was no one at the information desk. (location as a point)

We use at to describe locations including firms, companies, workplaces and educational institutions:

Did you once work at Intel?

The ancient manuscript, The Book of Kells, can be seen at Trinity College, Dublin.

Warning:

We say at school, at college but in class:

What did you study at college?

We’re not allowed to have mobile phones in class.

Not: … ~~at class~~.

We use at when we refer to an address:

The restaurant used to be at number 72 Henry Street.

We use at the to refer to public places where we get treatments, such as a dentist’s or doctor’s surgery, hairdresser’s or spa:

While Liz was at the dentist, I went shopping.

I read an interesting article about plastic surgery in a magazine when I was at the hairdresser’s.

At: group activities

We use at to refer to activities which involve a group of people:

I didn’t know anyone at the party.

There was a demonstration at the opening of the exhibition.

Good at, bad at

We use adjective + at to talk about things that we do well or badly:

I was never very good at sports.

She was always brilliant at drawing.

He was terrible at keeping his accounts in order.

At: numbers

In specific contexts, we use at with numbers.

Talking about prices:

At 80 pounds a night for a double room, the hotel is good value.

Talking about speeds:

According to the police, he was driving at 120 mph. (mph means ‘miles per hour’)

At: direction

We use at after a verb when we are talking about directing something towards another person or thing, often with verbs of perception and communication (smile at, shout at, wave at):

He threw the ball at the wall.

She was waving at the crowd.

At or at the

When we talk about buildings, we often use at the to refer to the building itself. When we refer to the activity that happens in the building, we don’t use the after at or in: