来自古英语 thaerfore,为了，因为，因此，来自 there,那里，fore,为了，来自 for 在古英语的 拼写变体。
英文词源
therefore (adv.)
Old English þærfore; from there + fore, Old English and Middle English collateral form of for. Since c. 1800, therefor has been used in sense of "for that, by reason of that;" and therefore in sense of "in consequence of that." Similar formation in Dutch daarfoor, German dafür, Danish derfor.
实用例句
1. The truth is that junk bonds were misnamed, and therefore misunderstood.
事实上人们对垃圾债券的称谓有误，所以产生了误解。
来自柯林斯例句
2. They had seen him trawling and therefore knew that there were fish.
他们曾见过他用拖网捕鱼，因此知道那里有鱼。
来自柯林斯例句
3. Men are anxious to improve their circumstances, but are unwilling to improve themselves; they therefore remain bound.--James Allen
人们总是渴望改善周遭环境，但是却不愿意改善自己，因此总停留在原地，无法进步。
来自金山词霸 每日一句
4. He's only 17 and therefore not eligible to vote.
他只有17岁，因此没有投票选举的资格。
来自《权威词典》
5. He lost his health, and therefore his difficulties increased.