Words and phrases that function as nouns, pronouns, proper nouns, numerals, adjectives or verbs can serve as the subject.
王老师：你的学生真聪明。
Wáng lǎo shī：nǐ de xué shēng zhēn cōng míng 。
Teacher Wang: Your students are really smart.
(你的学生 is a noun phrase.)
张老师：聪明没有用，努力最重要。
Zhāng lǎo shī ：cōng míng méi yǒu yòng ，nǔ lì zuì zhòng yào 。
Teacher Zhang: Being smart is of no use; being hard-working is most important.
(聪明 and 努力 are adjectives.)
[1] Yip, P. C., Rimmington, D., Xiaoming, Z., & Henson, R. (2009). Basic Chinese: a grammar and workbook. Taylor & Francis.
[2] Teng, W. H. (2016). Yufa! A practical guide to Mandarin Chinese grammar. Taylor & Francis.
