自
讲解
介词“自”用于引出时间或处所的起点，相当于“从”，常与“以来”“起”等搭配表示从某时开始，或表示从某地出发。
The preposition '自' is used to indicate the starting point of time or location, equivalent to 'from'. It often pairs with '以来' or '起' to express 'since' a certain time, or to indicate departure from a certain place.
例句
自1978年以来，中国发生了很大的变化。
Since 1978, China has undergone significant changes.
我们的航班准时自北京出发。
Our flight departs on time from Beijing.