So = so, so = so, so, so, it will be useful at the beginning of a sentence, or usually before summing up the summary of an article. This is a cohesive adverb, which can't be used in connecting sentences, so it should be used after conjunctions, for example, because of the flu, you can't come to the party. He has the flu, so he can't come to the party. There are usually more official ones, which will be used in papers and reports, and less oral ones. If it is not used to connect sentences, it can also be used in the middle of sentences. For example, there is a famous saying: I think I am here, and the explanation is: I think so I am. Therefore, this word has many uses and has a great chance of being used in spoken English. Americans like to use this word very much, but it will be counterproductive if it is not used well. I will explain later. It is a conjunction, which can be used to connect sentences or after conjunctions. It has many uses, such as: the manager was ill, so I went instead of her. The manager was ill, so I went to see him. He is very strong and suitable for this job. He is strong, so he is suitable for this job. Therefore, it is not a conjunction, nor can it be used to connect sentences. It is an adv. It is also an intersection adv like there. For example, therefore, your j can also be used at the beginning, middle or end of a sentence. He didn't work hard. So she was fired. He didn't work hard, so he was fired. Therefore, I will be able to repair the car without having to call the machinery. I have the ability to repair this car, so I don't need to find a mechanic. If you throw the ball as I demonstrated, you will have better luck to hit the target. When I show you, if you throw the ball in this way, you will have a better chance to hit the target. The above sentence is such a common method. By carefully comparing their usage, you should be able to understand them.