In an office or at the office? Why in different cases different prepositions are used? in an office: "He worked in an office in the town during most of the week" at the office: "Every Monday he told his friends at the office about his work on the car, but his news about it was never very good" come to the office (can I say come in the office) Then at last one Monday morning he came to the office and said to his friends, 'I have done it! A man was trying to build an electric motor-car. He worked in an office in the town during most of the week, but on Saturdays and Sundays he stayed at home in the country and worked on his electric car. Every Monday he told his friends at the office about his work on the car, but his news about it was never very good. Then at last one Monday morning he came to the office and said to his friends, 'I have done it! I have driven from my home to here by electricity!' His friends were all very glad. 'How much did it cost to get here by electricity?' they asked. 'Three hundred and two pounds,' he answered.