HSK 7-9
一来……，二来……
yī lái..., èr lái...
Firstly..., secondly...; for one thing...for another
Structure
Reason/Purpose 1 + 一来……，Reason/Purpose 2 + 二来……
How it works
This structure is used to list two or more reasons, purposes, or factors behind a decision or situation. It is more formal than '第一' and '第二', and while it usually appears as a pair, it can occasionally be followed by '三来' for a third point.
Examples
我决定搬到郊区住，一来环境清静，二来房租也便宜不少。
Wǒ juédìng bāndào jiāoqū zhù, yīlái huánjìng qīngjìng, èrlái fángzū yě piányi bùshǎo.
I decided to move to the suburbs; for one thing, the environment is quiet, and for another, the rent is much cheaper.
他选择出国深造，一来是为了增长见识，二来是想提高外语水平。
Tā xuǎnzé chūguó shēnzào, yīlái shì wèile zēngzhǎng jiànshì, èrlái shì xiǎng tígāo wàiyǔ shuǐpíng.
He chose to go abroad for further study, firstly to broaden his horizons, and secondly to improve his foreign language skills.
咱们合伙买这台仪器，一来能节省开支，二来大家都能用上。
Zánmen héhuǒ mǎi zhè tái yíqì, yīlái néng jiéshěng kāizhī, èrlái dàjiā dōu néng yòng shàng.
Let's buy this equipment together; first, it saves money, and second, everyone will be able to use it.
Common mistakes
Mixing '一来/二来' with '首先/其次' in the same sentence, which can sound redundant or disorganized.
Tip
Think of this pattern as providing a balanced justification for an action. It is often used when the speaker wants to show that a decision was well-thought-out from multiple angles.
More HSK 7-9 grammar
See 一来……，二来…… in real Chinese
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