Clause A, Subject + 则 + Clause B
The adverb 则 (zé) is a formal marker of contrast, similar to "however," "on the other hand," or "whereas" in English. It appears in the second clause of a pair to highlight a difference or alternative. For example, 他喜欢运动,她则喜欢读书 means "he likes sports, whereas she likes reading."
哥哥喜欢热闹,弟弟则喜欢安静。
gēge xǐhuān rènao, dìdi zé xǐhuān ānjìng.
The older brother likes excitement, while the younger brother prefers quiet.
大城市交通方便,小城市则空气更好。
dà chéngshì jiāotōng fāngbiàn, xiǎo chéngshì zé kōngqì gèng hǎo.
Big cities have convenient transportation, while small cities have better air.
年轻人爱刷短视频,老年人则更爱看电视。
niánqīngrén ài shuā duǎn shìpín, lǎoniánrén zé gèng ài kàn diànshì.
Young people love watching short videos, while older people prefer watching TV.