Usage note
严肃形容一个人表情认真，不随便笑，或者气氛很正式。
Yánsù xíngróng yīgè rén biǎoqíng rènzhēn, bù suíbiàn xiào, huòzhě qìfēn hěn zhèngshì.
Serious describes a person's expression as earnest, not casually smiling, or an atmosphere that is formal.
Context note
在学校里，老师有时会严肃地提醒大家遵守纪律。
Zài xuéxiào lǐ, lǎoshī yǒushí huì yánsù de tíxǐng dàjiā zūnshǒu jìlǜ.
At school, teachers sometimes seriously remind everyone to follow rules.
5 examples
爸爸的表情很严肃。
bà ba de biǎo qíng hěn yán sù。
Dad's expression is very serious.
老师严肃地说了安全问题。
lǎo shī yán sù dì shuō le ān quán wèn tí。
The teacher spoke seriously about safety issues.
他看起来有点严肃。
tā kàn qǐ lái yǒu diǎn yán sù。
He looks a bit serious.
会议的气氛很严肃。
huì yì de qì fēn hěn yán sù。
The atmosphere of the meeting is very serious.
不要总是那么严肃，笑一笑吧。
bú yào zǒng shì nà me yán sù， xiào yi xiào ba。
Don't always be so serious, smile a little.
5 mini stories
上课时，老师严肃地告诉大家要安静。同学们立刻坐好。
shàng kè shí， lǎo shī yán sù dì gào sù dà jiā yào ān jìng。 tóng xué men lì kè zuò hǎo。
During class, the teacher seriously told everyone to be quiet. The students immediately sat up straight.
小明的爸爸严肃地和他谈了一次话。小明认真听了。
xiǎo míng de bà ba yán sù dì hé tā tán le yí cì huà。 xiǎo míng rèn zhēn tīng le。
Xiao Ming's dad had a serious talk with him. Xiao Ming listened carefully.
在升旗仪式上，大家的表情都很严肃。没有人说话。
zài shēng qí yí shì shàng， dà jiā de biǎo qíng dōu hěn yán sù。 méi yǒu rén shuō huà。
At the flag-raising ceremony, everyone's expressions were very serious. No one spoke.
小红严肃地告诉朋友不要乱扔垃圾。朋友点了点头。
xiǎo hóng yán sù dì gào sù péng yǒu bú yào luàn rēng lā jī。 péng yǒu diǎn le diǎn tóu。
Xiao Hong seriously told her friend not to litter. Her friend nodded.
小刚在比赛前表情严肃，他深吸了一口气。然后开始跑步。
xiǎo gāng zài bǐ sài qián biǎo qíng yán sù， tā shēn xī le yì kǒu qì。 rán hòu kāi shǐ pǎo bù。
Xiao Gang had a serious expression before the race; he took a deep breath. Then he started running.
Mini dialogue
严肃的老师
A
王老师看起来很严肃。
Wáng lǎo shī kàn qǐ lái hěn yán sù.
Teacher Wang looks very serious.
B
是的，但他其实很关心我们。
Shì de, dàn tā qí shí hěn guān xīn wǒ men.
Yes, but he actually cares about us a lot.
严肃的话题
A
我们谈点严肃的事情吧。
Wǒ men tán diǎn yán sù de shì qíng ba.
Let's talk about something serious.
B
好的，关于环保问题，我们需要认真对待。
Hǎo de, guān yú huán bǎo wèn tí, wǒ men xū yào rèn zhēn duì dài.
Okay, regarding environmental issues, we need to take them seriously.
Related words and contrasts
similar
认真
rèn zhēn
earnest, serious
认真 is more about being conscientious and careful, while 严肃 is about a stern or solemn manner.
related
严格
yán gé
strict
严格 means strict in rules or standards, often used for people or requirements.
opposite
轻松
qīng sōng
relaxed
轻松 is the opposite of serious, meaning light-hearted or relaxed.