HSK 5
连接分句或句子：从而、加上、完了、一旦
lián jiē fēn jù huò jù zi ： cóng ér 、 jiā shàng 、 wán le 、 yí dàn
Connecting clauses or sentences: 从而, 加上, 完了, 一旦
Explanation
This is a group of conjunctions (words that link clauses) used to join clauses, each expressing a different logical relationship: 从而 (cóng'ér) = thereby/thus, 加上 (jiāshàng) = in addition, 完了 (wánle) = after that/then, 一旦 (yídàn) = once.
[cause]，从而 + [result]; [reason 1]，加上 + [reason 2]，[conclusion]; [task 1]，完了 + [task 2]; 一旦 + [condition]，就 + [result].
从而 links a result/goal achieved thanks to the preceding clause, leaning toward written language. 加上 adds one more reason leading to a conclusion. 完了 is used in colloquial speech, indicating the next action after the previous one is done. 一旦 introduces a hypothetical condition, usually paired with 就 in the following clause.
从而 stresses a cause-effect relationship with a positive result; 加上 is merely an accumulation of reasons, not carrying a direct causal meaning. 完了 (after that) differs from 完了 meaning "it's ruined/we're doomed" in other contexts; you need to look at the situation.
With 一旦, learners very often forget the accompanying 就 clause (correct: 一旦选择了就不能放弃). Don't use 从而 for a plain "and then" relationship in speech (使用 完了/然后 is more natural). 加上 goes at the head of the added clause, not at the end of the sentence.
Examples
He studied hard, and thereby realized his dream of becoming a translator.
The weather isn't very good today, and on top of that you still have a lot of homework, so let's not go to the park after all.
Hurry up and finish your homework; after that we'll go play at the park.
You need to think it over carefully; once you've chosen, you can't give up.
Practice
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Learn “连接分句或句子：从而、加上、完了、一旦” effectively
The grammar point “连接分句或句子：从而、加上、完了、一旦” (Connecting clauses or sentences: 从而, 加上, 完了, 一旦) is one of the key structures at HSK 5. To use it fluently, you need to understand the contexts where it's used and practice regularly.
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