The preposition 自
The preposition 自 has two different meanings with two different functions.
The meaning “from”
自 
indicates the place from where an action started. Sometimes it may be omitted when translating into English.
In a sentence we should state 自 before a noun that denotes a place.
indicates the place from where an action started. Sometimes it may be omitted when translating into English.
In a sentence we should state 自 before a noun that denotes a place.Scheme
subject
自
place
predicate
Examples
我们明天自北京出发
We leave from Beijing tomorrow
wǒmen míngtiān zì běijīng chūfā
自梯子跌落
To down the stairs
zì tīzi diēluò
We often use 自 in the construction 自…到… .
.Examples
旅客自机场改乘出租汽车到旅馆
The passengers take a taxi from the airport to the hotel
lǚkè zì jīchǎng gǎi chéng chūzūqìchē dào lǚguǎn
The meaning “starting from”
Sometimes 自 can be used to express the starting point of an action in the past. It can be translated as “ever since/since”.
After expressing the time, we should use the following words:
后 or 以后
起 or 开始
以来
or 以后
起 or 开始
以来 Scheme
subject
自
time
predicate
Pay attention
We can state the subject before 自 or after the adverbial modifier of time.
Examples
自去年以来，我们的问题变大了
Since last year, our problems have gotten bigger
zì qùnián yǐlái, wǒmen de wèntí biàn dà le
她自回复以后活得更有劲了
She has come back to life much more vigorously since her reply
tā zì huífù yǐhòu huó de gèng yǒujìn le
In this meaning, we also can use 自 in the construction 自…到….
Examples
自一九四零年到现在
from1940 to the present
zì yī jiŭ sì líng nián dào xiànzài