"Since then" in Engpsh can be translated as "自那以后" and is commonly used to refer to a specific event or time period in the past. This phrase is often used to describe something that has happened or changed since that time.
Example sentence in Engpsh:
Since then, I've learned a lot about the topic.
Example sentence translation in Chinese:
自那以后，我对这个主题有了很多了解。