Prepositions in Chinese
A preposition (介词) is an auxiliary part of speech that expresses a relationship between words in phrases and sentences.
Prepositions in Chinese are used to indicate the direction of an action or the position of an object.
Examples
给父母写信
to write a letter to your parents
gěi fùmǔ xiě xìn
在上海
in Shanghai
zài shànghǎi
Prepositions are used to express how an action is performed.
Examples
用刀叉吃东西
to eat with a knife and fork
yòng dāochā chī dōngxi
Moreover, prepositions can be used to indicate the future.
Examples
产量将下降6%
Manufacturing will fall by 6%
chǎnliàng jiāng xiàjiàng bǎifēnzhī liù
Prepositions are usually placed before an adjunct and complement. So, the most common structure looks like this:
Scheme
subject
who? what?
preposition
adjunct/complement
predicate
action
Pay attention
The above structure can be changed depending on the specific preposition.
Examples
我不常给父母写信
I don’t often write to my parents
wǒ bù cháng gěi fùmǔ xiě xìn
老师住在上海
The teacher lives in Shanghai
lǎoshī zhù zài shànghǎi
If there is a preposition in a sentence, negative determiners and some adverbs are mostly placed before this preposition, not before the predicate.
Examples
他不对我说话
He doesn’t talk to me
tā bú duì wǒ shuōhuà
花瓶也被打破了
The vase was also broken
huāpíng yě bèi dǎpò le
Prepositions are often used to form Chinese structures.
For example, 从…到… 
or 因为…所以… .
or 因为…所以… .Examples
我们从8点到11点上课
We have lessons from 8:00 to 11:00
wǒmen cóng bā diǎn dào shíyī diǎn shàngkè
因为天气很冷，所以得多穿点儿衣服
Wrap yourself up warmly. It is cold outside
yīnwéi tiānqì hěn lěng, suǒyǐ děi duō chuān diǎnr yīfu