Another very interesting grammar point from my favourite Mandarin grammar book.
“Modern Mandarin Chinese Grammar” by Claudia Ross and Jing-heng Sheng Ma 2006 Routledge
Noun phrase omission
In English, when a series of noun phrases refer to the same entity, all instances after the first reference typically occur as pronouns. In Mandarin it is more common to simply omit the noun phrase when it needs to be repeated in a sentence, BUT only when it occurs in the same grammatical role as the first instance.
In this example, the first reference and the omitted noun phrases are subjects of the verb.
Zhāng měilì měi tiān dū hěn máng ( – ) zǎoshang liù diǎn qǐchuáng, ( – ) qī diǎn chūmén, ( – ) wǎnshàng jiǔ diǎn cái huí jiā.
Meili Zhang is very busy every day. She gets up at 6 o’clock, she leaves the house at 7 o’clock, and she doesn’t get home at night until 9 o’clock.
In this example, the first reference and the omitted noun phrase are objects of the verb.
Tā mǎile qúnzi, dàojiā yǐhòu mǎshàng chuān shàngle ( – ).
She bought a skirt, when she got home she immediately put it on.
When a noun phrase with identical reference occurs in a different grammatical role from the first instance, it occurs as a pronoun and is not omitted. In this example, the first reference is the object of 喜欢 xǐhuan ‘to like’. In the second reference, it is the subject of the sentence.
Wǒmen dōu xǐhuan nàgè háizi, tā yòu kě’ài yòu guāi.
We all like that child. She is both cute and well-behaved.