As a general rule, in the Chinese language, the subject in a sentence should be definite. However, an indefinite noun that is generic can serve as the subject as well.
一个人不能没有良心。
yī gè rén bú néng méi yǒu liáng xīn 。
A man cannot be without conscience.
(一个人 means ‘any man’, not ‘a certain man’. It is ‘generic’and can serve as the subject.)
(Incorrect: 一个人在等你。)
Correct: 有一个人在等你。 yǒu yī gè rén zài děng nǐ 。
A man is waiting for you.
(一个人 means ‘a certain man’. It is indefinite; therefore, it cannot serve as the subject.)
学生应该用功。
xué shēng yīng gāi yòng gōng 。
Students should be diligent.
(学生 is generic.)
那个学生很用功。
nà gè xué shēng hěn yòng gōng 。
That student is diligent.
(那个学生 is definite.)
熊猫很可爱。
xióng māo hěn kě ài 。
Pandas are cute.
(熊猫 is generic.)
[1] Yip, P. C., Rimmington, D., Xiaoming, Z., & Henson, R. (2009). Basic Chinese: a grammar and workbook. Taylor & Francis.
