## Difference between Therefore and So

The question in my book is as follows

Add **so, therefore** where appropriate

1. He worked hard, _______ he could earn much money. (answer: therefore)

2. He's been studying really hard, _______ he can pass the exams. (answer: so)

The answer key in my book is 1) therefore; 2) so.

I am confused about the difference between therefore and so. Could you explain to me? I have read some other grammar book that therefore and so can be used interchangeable. However, this book they distinguish therefore and so without giving any explanations.

Can you give some more examples to show the difference between therefore and so. Thank you.

I'm with Paul on the difference between therefore and so, but don't agree with your textbook authors. Either word could be used with either sentence, and with slightly different meanings.

Why did he work hard?

1. He worked hard, **so** he could earn much money. = He worked hard in order to earn a lot of money. = He worked hard for the purpose of earning a lot of money.

Why could he earn a lot of money?/ Why (how) was he able to earn a lot of money?

1. He worked hard, **therefore** he could earn much money. = He worked hard and, consequently, he could earn a lot of money. = He worked hard, and as a result, he was able to earn a lot of money. = He worked hard, that's why he could earn a lot of money.

Why has he been studying really hard?

2. He's been studying really hard, **so** he can pass the exams. = He's been studying really hard, in order to be able to pass the exams. = He's been studying really hard for the purpose of passing the exams.

Why can he pass the exams?

2. He's been studying really hard, **therefore** he can pass the exams. = He's been studying really hard, and, consequently (as a result), he can pass the exams. = He's been studying really hard, and for that reason (that's why) he will be able to pass the exams.

In summary:

so = for the purpose of, in order to

therefore = and as a consequence, and as a result, and that's why, and for that reason