1.At can indicate location     

Pattern 1: at + the + place within a city or town
The women are at the supermarket.                                        

Nouns commonly used with this pattern:
apartment, bus stop, factory, hospital, hotel, house, mall, office, park, parking lot, restaurant, station, store, theater, university

Pattern 2: at + an address

She lives at 3757 North 52nd Street, apartment 10.
You can contact him by e-mail, @xyz.com
(The symbol @ is pronounced ''at.")                                          

Pattern 3: at + the + place within another place
He was waiting in the room at the door.
He likes to sit in her apartment at the window facing the park.            

Nouns commonly used with this pattern:
counter, desk, table, window                           

2.At indicates a place of attendance.              

Pattern 1: be + at + Æ place or meal of regular attendance
The children are at school.
We aren't allowed to watch television when we are at dinner.              

Nouns used with this pattern:
church, class, home, practice, school, work
breakfast, lunch, dinner                                              

Pattern 2: be + at + noun of event
They are at the movies.
She is at a meeting.                                        

 Nouns commonly used with this pattern:
breakfast, brunch, celebration, concert, conference, dance, debate, dinner, forum, function, funeral, game, lecture, luncheon, meeting, movies, parade, party, play, program, reading, reunion, show, wedding  

3.At can indicate in the direction of; toward.            

Pattern 1: verb + at + noun
The teacher smiled at the new girl.                  

 Verbs commonly used with this pattern:
aim, frown, glare, grab, grin, growl, hit, howl, laugh, leer, look, rush, shoot, shout, slap, smile, snatch, stare, swear, swing, wink, yell                                                                                                                     

Pattern 2: verb + noun + at + noun
The small boy threw a rock at the window.                 

Typical verbs:
swing, throw, toss       

Expression with this meaning:      

make a pass at—indicate romantic interest toward
The young man made a pass at the beautiful woman he met at the party.                   

4.At is used to express time.                

Pattern: at + specific time
We are leaving at four thirty.
They went home at midnight.
We always eat lunch at noon.              

Expressions with this meaning:               

at first—when something started
At first we thought this hike would be easy.                

at night—when it is night
I always read or study at night.           

at once—immediately (see also number at a time, below)
We must pack up and leave at once.                                       

at present—now
At present they are sleeping.               

at last—finally
After that long drive, we are home at last.        

at length—for a long time, thoroughly
We discussed that topic at length at our meeting.       

at the beginning—at first, when something started
At the beginning we tried to go too fast.                      

at the end—when something ended
At the end of the story, everybody was happy.            

at the moment—at present, now
I am very busy at the moment.            

at the sound, thought, or prospect of—when one experiences
She gets nervous at the sound of his voice.
We shudder at the thought of moving again.
He is excited at the prospect of going to South America.                     

(number) at a time—ratio per instance or unit
The tall boy liked to go up the steps two or three at a time.                 

at once—several things together
Try to learn one step at a time, rather than three or four at once.                     

5.At can mean busy using something; working.                

Pattern 1: at + the + noun
I have been at the computer all day.                

 Nouns often used after at the:
cash register, computer, fax machine, ironing board, sewing machine, stove, (steering) wheel                      

Pattern 2: be + at + work
be + at + it
You must not bother him; he is at work.
He has been at it for four hours.                 

Expression:
keep at it—not stop working
He wanted to go home, but he kept at it until the work was finished.               

6.At can indicate a condition.             

Pattern: be + at + Æ noun
Those two countries have been at peace for ten years.            

Nouns used after at:
attention, ease, peace, rest, risk, war              

Expression:
sick at heart—sad
We were sick at heart when the dog died.        

7.At can indicate reaction.                      

Pattern 1: adjective of state + at + noun
We were shocked at the condition of the classrooms.             

 Typical adjectives used before at:
aghast, amazed, astonished, astounded, indignant, shocked, speechless, surprised, thrilled, upset              

Pattern 2: verb + at + noun
The crowd rejoiced at the good news.             

Verbs commonly used before at:

cheer, grumble, guess, hint, hoot, laugh, rebel, rejoice, snort, tremble                       

8.At indicates a degree of skill.                   

Pattern 1: adjective + at + noun
Your son is good at tennis, but not very good at hockey.        

Pattern 2: adjective + at + verb in gerund form
That couple is really great at dancing the tango.         

Typical adjectives used before at:
bad, excellent, good, great, lousy, skilled, terrible                  

Expression:
be an old hand at—be very experienced with Our professor is an old hand at government operations.              

9.At can indicate a rate or level      

Pattern 1: at + noun indicating price
At the market they are selling apples at sixty-nine cents a pound.
I wish we could buy mangoes at that price.
Her husband tries to buy everything at a discount.                                          

Pattern 2: @^* + number + a + noun indicating a unit of measurement
They are selling apples @ 69 ¢ a lb.                                                                            

Pattern 3: at + noun indicating level of age or distance
You shouldn't work so hard at your age.
He was still singing at (the age of) eighty.
We can't see very well at this distance.
The plane was flying at three thousand feet.                            

Expressions:
at a distance—from far away
I saw the new baby at a distance, and he looked beautiful.
at arm's length—not close
I try to stay at arm's length from him to avoid an argument.                

Pattern 4: at + noun indicating level of speed
She shouldn't drive at that speed.
At twenty-five miles an hour on the freeway, she should get a ticket.               

Exception: When speed is expressed in numbers after a verb, at is omitted.
That driver is going eighty miles an hour.
He drove sixty miles an hour the whole way home.                                                     

10.At can indicate the highest possible degree in value.        

Pattern: at + superlative adjective used as noun
At best she is an adequate typist.
At least she comes to work every day.
You should be here by five o'clock at the latest.                      

Superlatives commonly used with this pattern:

best, least, most, worst
the earliest, the latest                                                   

11.Expressions                    

be at an advantage—be in a better-than-average position
He is at an advantage because his family has influence.          

be at a disadvantage—be in a less-than-average position
When you are a newcomer at work, you are at a disadvantage.            

down at the heels—shabby
His brother looked down at the heels when he was without work.       

at one's mercy—in someone else's power
I was at the intruder's mercy because he had a gun in my back.         

at one's discretion—someone's own decision
We can go home when we are ready, at our own discretion.                

at that—                   

    1. at that point, not any more or further
    You did a good job; leave it at that.                 

    2. illogically
    We got lost, and in our hometown at that!                   

be getting at—meaning, but not saying
The manager didn't exactly say his employer had been dishonest, but we all knew what he was getting at.                

12.Phrasal verb                  

pick at something (nonseparable)—try to remove something with one's fingernails
The child picked at the scab on his knee.      

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