1. indicATes position: at is used to indicate the specific position of people or things. I am a hornet's nest. The cat is by the window. )

2. time: AT is used to indicate a specific time point or time period. We have a meeting at three o'clock. Sheworksatnight。 She works at night. )

3. Express price: AT is used to indicate the price of goods or services. That shop sells for 20 dollars. Shirts in that store cost $20. The movie ticket to the cinema is 10 dollars. The price of movie tickets in the cinema is $ 10. )

4. Indicating activities or events: AT is used to indicate the location where activities or events occur. The concert was held in the park. The party was held at her house. )

5. express goals or objectives: AT is used to express the goals or objectives of someone or something. Hestudieshardatschool。 Sheworkshardatherjob。 )

6. state or situation: at is used to indicate the state or situation of someone or something. He is good at playing the guitar. She is not good at math. )

7. Show connection or connection: AT is used to indicate the connection or connection between someone or something and others or objects. The cat is scratching at the door. Both ends of the wire are connected. )

8. Express proportion or ratio: AT is used to express proportion or ratio. For example, the company overestimated by 30%. (The company's rounds are overvalued by as much as 30%. ) There is a recipe that requires two cups of sugar at a time. )

9. Express speed or rate: AT is used to express speed or rate. For example, cars travel at a speed of 60 miles per hour. The car is driving at a speed of 60 miles per hour. )Hetypedatafastpace。 He can type quickly. )

In a word, AT is a multifunctional preposition, which can be used to express position, time, price, activity, goal, state, connection, proportion and speed. According to the specific context, the specific usage and significance of AT can be determined.