1. at 1）用于表示在时间的某一点或某一时刻.例如: What were you doing at this time yesterdayStudents often start classes at eight o'clock in the morning. 2）用于表示在三餐或中午、晚上.例如: What did your mother say at breakfast ／lunch ／supper timeWe heard a girl singing in the next room at noon ／night.