HSK 4
Correct

不得不 vs 得

/ bùdébù vs děi /
Strokes
https://i.cchatty2.com/filters:format(webp)/fit-in/684x0/img/202005/不得不vs得-Chinese-grammar-Cchatty-yyyy-1589851735.jpg

Formula

1
不得不 + Verb
2
得 + Quantifier

Definition

不得不 is Adverb (副词), means "have to"

 

得 is Optative Verbs (能愿动词), means "should"

Example

Only 不得不 is used.
不得不 means "have to",
"不得不 + Verb" is often used to emphasize somebody has to do something he/she didn't want to do due to the environment or condition.
不得不 + Verb
1
不得不
xiě
zuò
作业
  

He has finished his homework.

2
kuài
chídào
迟到
le
  
,
suǒ
所以
不得不
zuò
chūchē
出租车
  

I'm going to be late, so I have to take a taxi.

Only 得 is used - 1
To indicate one needs or wants to do something.
3
Tài
wǎn
le
  
,
děi
zǒu
le
  

It's too late. I have to go.

4
yǒudiǎnr  
有点儿
lèi
  
,
de
xiūxi
休息
le
  

I'm a bit tired. I need to rest.

Only 得 is used - 2
To indicate one should do something according to social conventions.
5
Rénrén
人人
dōu
de
zūnshǒu
遵守
法律
  

Everyone must obey the law.

6
Guò
马路
de
xiǎoxīn
小心
  

When crossing the road, you'd be careful!

Only 得 is used - 3
To indicate one needs to do something considering certain facts.

1) To indicate one needs to do something that has been scheduled in advance.
2) It is used to give advice.
3) "得 + Quantifier" is used to estimate a quantity, particularly that of time or money.
得 + Quantifier
7
Xià
下午
men
我们
děi
kāihuì
开会
  

We have to have a meeting this afternoon.

8
Yào
xià
下雨
le
  
,
děi
dài
sǎn
  

It's going to rain, you'll have to take an umbrella.

9
Zhège
这个
bāo
de
200
200
měiyuán
美元
  

This bag costs $200.

Exercise

Fill in the blanks with 不得不 or 得:

 

1.今天他( )穿西装,因为今天有晚会。

2.手机没电了,马上充电了。

3.今天是星期六,但是明天有HSK考试,所以我( )学习。

4.医生要病人锻炼,病人( )锻炼。

5.五点了,我( )去做运动了。

6.这件衣服太贵了, 虽然我非常喜欢,但是( )放弃。

7.从上海到北京坐飞机( )两个小时。

8.这张电影票( )100块钱。