Formal Conjunctions with 以
以便, 以免, and 以致 are formal connectors expressing purpose, avoidance, and unintended consequence.
Pattern
Clause A + 以便/以免/以致 + Clause B
Explanation
These three conjunctions share the literary morpheme 以 (meaning 'so as to') but serve distinct functions. 以便 means 'so that/in order to' (positive purpose), 以免 means 'so as to avoid/lest' (negative purpose), and 以致 means 'so that/resulting in' (unintended negative consequence).
All three belong to formal written registers and are common in official documents, academic writing, and news reports. In spoken Chinese, simpler alternatives like 好让, 免得, and 结果 are preferred. Note that 以致 almost always introduces an undesirable outcome.
Examples
请提前通知我们，以便做好准备。
Qǐng tíqián tōngzhī wǒmen, yǐbiàn zuò hǎo zhǔnbèi.
Please notify us in advance so that we can prepare.
出门带伞，以免淋雨。
Chūmén dài sǎn, yǐmiǎn lín yǔ.
Bring an umbrella when going out, lest you get caught in the rain.
他长期熬夜，以致健康严重受损。
Tā chángqī áoyè, yǐzhì jiànkāng yánzhòng shòusǔn.
He stayed up late for a long time, resulting in serious damage to his health.
Common Mistakes
他努力学习，以致考上了大学。
他努力学习，以至于考上了大学。
以致 is used for negative consequences. For positive results, use 以至于 or restructure the sentence.
以免他不来。
以免他迟到。
以免 already implies avoidance, so do not add negation in the following clause.
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