at+ the+ place = at the super market

at +  an adress

at+ Place of attendance= the children are at school

at+ events= at the movies, at a meeting

at + in the direction of, toward=  The teacher smiled at the new girl

at+ specific time= at noon

at+ condition= at peace, at risk

sick at heart = sad

after reaction = shocked at the condition

rejoiced at the good news

be at an advantage= be in better than avarage position

He is at an advantage because his family has influence.

When you are  a newcomer at work, you are at a disadvantage.