以…为由
on the grounds of; citing … as the reason
Structure
主语 以 理由 为由 动词
What it means
On the grounds of; citing … as the reason. It often hints that the stated reason may be an excuse.
How it is built
Subject + 以 + reason + 为由 + action: 他以身体不适为由，拒绝了邀请 (He declined the invitation on the grounds of ill health).
When to use it
Formal; common in news for refusals and restrictions. Same frame: 以…为借口 (as a pretext, openly doubtful), 以…为名 (in the name of). Plain 因为 just gives a cause, with no doubt implied.
Watch out
The reason sits between 以 and 为由: ✗ 他为由身体不适 ✓ 他以身体不适为由. Since it can sound doubtful, use 因为 for a reason you fully accept.
Examples
美国以国家安全为由，限制向中国出口先进芯片。
Citing national security, the United States restricts exports of advanced chips to China.
他以身体不适为由，拒绝了邀请。
He declined the invitation on the grounds of ill health.
Learn this in Lesson 106 · HSK 7–9: 芯片与人工智能 (Chips and artificial intelligence)
A dialogue, a reading, word cards with audio and a drill that uses it, in Learn Chinese with Bao. The first lessons of every level are free.
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