Inactive Tutor answered • 04/06/21
While both 由 and 被 are used to mark the "doer" of an action, they have different meanings and are used in different contexts.
1. 由 is often used in sentences to emphasize WHO is going to do it.
昨天你开车，今天由我开吧。(You drove yesterday. Today's my turn.)
这件事由我说不太合适，由你来说吧。(It's not suitable for me to talk about this matter. Why don't you do it instead?)
这是他的错，当然由他负责。(It was his fault, of course he should take responsibility for it.)
You can probably memorize a few words that often come with 由:
由...负责
由...说明
由...决定
由...解决
由...当
One final trick for you: in all of the cases above, you can take off the 由 and it would not really affect the core meaning of the sentences. 由 is only there to make people pay attention to the doer of the action.
被 is very different in this sense. You usually can't take out 被 and still make a sentence work the same way.
2. 被 is used in passive voice sentences. In Chinese, passive voice sentences are far less common than in English. Usually, they are used to describe unfortunate situations. Consider these classic examples:
我的作业被狗吃了。(My homework was eaten by my dog.) (I did not want this to happen.)
这件事被他知道了。(The matter was found out by him.) (It was not in our plan.)
Even though 被 can be used in positive ways, but those cases are usually very specific and not all that common. It's best for you to learn them case by case.
谁都需要被爱、被接纳。(Everyone needs to be loved and accepted.)
他被领导表扬了。(He was praised by the leader.)
Here, 负责 (take responsibly) is definitely positive, and not one of those special cases in which 被 could be used in a positive sense. Using 由 is way more natural.
