Preposition 由 — Introducing the Agent
介词：由²
Use the preposition 由 to indicate who is responsible for or carries out an action
Place 由 before the person or group responsible for performing an action. The verb 来 or 去 often appears after the agent to soften the assignment or suggestion. 由 can also directly precede the verb without 来/去 in more formal contexts.
由 in this usage is different from 由 meaning "from" (a place). Here it assigns agency — it tells us who does the action. It is more formal than 让 and emphasizes responsibility or authority rather than simple permission.
Lesson Targets
Podcast
Podcast: Preposition 由 — Introducing the Agent (介词：由²)
Listen to Jason & Amy explain the 介词：由² pattern
New here?
Understanding 介词：由²
The preposition 由 (yóu) is a formal and elegant way to specify who is responsible for doing something. While 让 simply means "let someone do something," 由 carries a stronger sense of assignment, delegation, or responsibility. When a teacher says 这道题由你来回答, they are not just asking — they are designating you as the person responsible for answering. In workplace and organizational contexts, 由 is extremely common: tasks are assigned, projects are led, and decisions are made using this structure. The pattern often includes 来 after the agent, which softens the tone and makes the assignment feel more like an invitation than a command. Mastering 由 will make your Chinese sound more professional and precise, especially in formal discussions, meeting summaries, and written reports.
Key Points
- 由 (yóu) = "by" — introduces the agent (the doer) of an action.
- 由 + person + 来 + verb is the most common spoken pattern.
- 由 + person + 负责 (fùzé) means "to be in charge of / responsible for."
- 由 is more formal than 让 and implies delegation or authority.
- In passive-like sentences, 由 focuses on who does it, while 被 focuses on what was done to the subject.
- 由 can also introduce a cause or origin: 由此可见 (from this we can see), but that is a different usage.
In Chinese workplace culture, clarity about responsibility is highly valued. Using 由 to assign tasks is common in meetings and official documents. It reflects a structured, hierarchical approach to work where each person has clearly defined duties. You will hear 由 frequently in news broadcasts, government announcements, and corporate communications.
Key Vocabulary
Example Sentences
这道题由你来回答吧。
This question — you answer it.
由 + agent + 来 + verb: assigning a task
这件事情由班长负责。
This matter is the class monitor's responsibility.
今天的会议由王经理主持。
Today's meeting is chaired by Manager Wang.
这个项目由我们部门来完成。
This project will be completed by our department.
晚饭由谁来做？
Who will make dinner?
Question form: 由谁来 + verb
孩子的教育不能只由学校负责。
Children's education cannot be the responsibility of schools alone.
下一步的计划由大家一起讨论决定。
The next step of the plan will be discussed and decided by everyone together.
费用由公司承担。
The costs are borne by the company.
Formal: 由 + agent + verb, no 来
Common Mistakes
Do not combine 让 and 由 together. 由 already introduces the agent — adding 让 is redundant.
由 must come before the agent, not after. The word order is 由 + person + 来 + verb.
由 introduces the active doer, not the passive receiver. For passive constructions, use 被.
Practice Exercises
Tips & Tricks
Think of 由 as a spotlight — it shines on the person who is doing or responsible for something.
When you hear 由……负责, it almost always means a formal assignment of responsibility.
In casual speech, 让 is more natural. Save 由 for formal, workplace, or written contexts.
Practice by describing who does what in your school or workplace: 卫生由值日生负责, 教学由老师负责.
Homework
Write six sentences using 由 to describe responsibilities in your school, workplace, or family. For each sentence, specify who is responsible for what task. Try using both 由……来…… and 由……负责 patterns.