Modal verbs: have to, must

Chinese modal verbs that express necessity are: 要 (yào), 应该 (yīnggāi), 得 (děi), 需要 (xūyào) and 必须 (bìxū).

要 (yào) is used in the imperative form, whose negation is expressed with 不要 (bùyào) or 别 (bié). It also expresses an objective necessity.

你不要动！/你别动！
nǐ bùyào dòng/nǐ bié dòng
[you not to-have-to move]
Don’t move!

你要好好地学习才能考上。
nǐ yào hǎohǎo dì xuéxí cáinéng kǎo shàng
[you have-to good ST to-study then-and-only-then can pass-an-exam]
You have to study hard in order to pass the exam.

应该 (yīnggāi) expresses the conditional form and it is equivalent to “should”. It indicates a conjecture or a suggestion.

医生说，你不应该抽烟。
yīshēng shuō, nǐ bù yìng gāi chōuyān
[doctor to-say, you not should to-smoke]
The doctor said you should not smoke.

这个手机应该是我叔叔的。
zhège shǒujī yìng gāi shì wǒ shūshu de
[this QU mobile-phone should be I uncle ST]
This mobile phone should be my uncle’s.

你应该多多看书。
nǐ yīnggāi duōduō kànshū
[you should more to-read]
You should read more.

得 (děi) expresses a necessity.

我得回家。
wǒ děi huí jiā
[I must to-go-back home]
I must go back home.

需要 (xūyào) means “to need” and expresses an objective necessity.

我需要你的帮助。
wǒ xūyào nǐ de bāngzhù
[I to-need you ST help]
I need your help.

必须 (bìxū) expresses an objective necessity, and an absolute need.

你买东西的时候，必须付钱。
nǐ mǎi dōngxī de shíhòu, bìxū fù qián
[you to-buy thing ST time, to-have-to pay money]
When you buy something, you have to pay.

Cover background picture by Ling Tang (unsplash.com)