乘 + Condition/Noun
乘 (chéng) is a Chinese verb meaning "to take advantage of" an opportunity or condition. It is commonly used in literary or set expressions to indicate doing something while a favorable condition exists, as in 乘凉 (to enjoy the cool).
我们乘天气好赶紧出发吧。
wǒmen chéng tiānqì hǎo gǎnjǐn chūfā ba.
Let's take advantage of the good weather and set off right away.
他乘大家不注意,悄悄地离开了。
tā chéng dàjiā bù zhùyì, qiāoqiāo de líkāi le.
He slipped away quietly while no one was paying attention.
乘现在还有时间,把作业写完吧。
chéng xiànzài hái yǒu shíjiān, bǎ zuòyè xiě wán ba.
While there's still time, finish your homework.