A preposition is used to link nouns, pronouns and phrases to other words in a sentence. The word or phrase that the preposition introduces is called the object of the preposition. A preposition is used to indicate the temporal, spatial or logical relationship of its object to the rest of the sentence. Here are some examples of the prepositions “at” and “in”:

Preposition AT

Used to indicate a specific time:

• I will be there at 12 p.m.
• He reported for duty at 1300.
• My father will be here exactly at 3:30 p.m.

Used to indicate a place:

• We will meet at my house.
• There will hundreds of people at the outdoor concert.
• We went to a baseball game at the stadium.
• She is studying at Virginia State University.
• The doctor works at the hospital.

Used to indicate a destination:

• The children arrived at school.
• The waiter was at our table to take our order.
• I left the rental car at the dealership.

Used to indicate a direction:

• The dog jumped at the intruder.
• The policeman leaped at the criminal.
• The pitcher threw the baseball at third base.

Prepositions IN

Used for unspecific times during a day, or a month, or a season, or a year:

• He always drinks a cup of coffee in the morning.
• We are going to married in July.
• In the summer, we have the least amount of rain.
• We went swimming in the ocean last year.

Used to indicate, or point out, a location or place:

• The man looked in wallet and pulled out some money.
• While visiting the ocean, we stayed in a rental cottage.
• I live in Chesapeake, Virginia.

Used to indicate a shape, color, or size:

• The painting is in the style of Rembrandt.
• The soldiers stood in formation.
• My dog is very small in size.

Used to tell us the noun is completely, or partially in an enclosed space (surround or closed off on all sides):

• The cat is hiding in the box.
• The table is in the center of the room.
• I live in the city.

Used to indicate the direction of something by adding “to”:

• IN + To = into: signifies movement toward the interior of a volume.
• The frog jumped into the water.