Usage note
由表示由某人或某事负责，也可表示通过。
yóu biǎo shì yóu mǒu rén huò mǒu shì fù zé， yě kě biǎo shì tōng guò。
由 means by someone or something, or through.
Context note
由常用于正式表达、来源和负责。
yóu cháng yòng yú zhèng shì biǎo dá 、 lái yuán hé fù zé。
由 is often used in formal writing, sources, and responsibility.
5 examples
这件事由老师负责。
zhè jiàn shì yóu lǎo shī fù zé。
This matter is handled by the teacher.
由我来决定。
yóu wǒ lái jué dìng。
Let me decide.
这个故事由他讲。
zhè ge gù shì yóu tā jiǎng。
This story is told by him.
由此可见。
yóu cǐ kě jiàn。
It can be seen from this.
活动由学校安排。
huó dòng yóu xué xiào ān pái。
The activity is arranged by the school.
5 mini stories
这次活动由学生会组织。
zhè cì huó dòng yóu xué shēng huì zǔ zhī。
This event is organized by the student union.
由他带队，大家都放心。
yóu tā dài duì， dà jiā dōu fàng xīn。
With him leading the team, everyone feels at ease.
问题由老师来解释。
wèn tí yóu lǎo shī lái jiě shì。
The teacher explains the problem.
这张票由我来买。
zhè zhāng piào yóu wǒ lái mǎi。
I will buy this ticket.
由此可以看出，练习很重要。
yóu cǐ kě yǐ kàn chū， liàn xí hěn zhòng yào。
From this, we can see that practice is important.
Mini dialogue
谁做的蛋糕
A
这个蛋糕是由谁做的？
Zhège dàngāo shì yóu shéi zuò de?
Who was this cake made by?
B
这个蛋糕是由奶奶做的。
Zhège dàngāo shì yóu nǎinai zuò de.
This cake was made by grandma.
选班长
A
班长是由大家选出来的吗？
Bānzhǎng shì yóu dàjiā xuǎn chūlái de ma?
Is the class monitor chosen by everyone?
B
是的，由全班同学投票。
Shì de, yóu quán bān tóngxué tóupiào.
Yes, by a vote of the whole class.
Related words and contrasts
similar
被
bèi
by (passive marker)
Also marks the doer in a passive sentence, but 由 often focuses on who is responsible.
contrast
从
cóng
from
Means 'from' a place or time, while 由 can mean 'by' a person.