If vs. Unless

Read the following sentences.

• Work hard. Otherwise you will not pass.

These two sentences can be combined into one using if or unless.

• If you work hard, you will pass. OR If you do not work hard, you will not pass.
• Unless you work hard, you will not pass.

• He must carry out my orders. Otherwise he will be sacked.

We can combine these two sentences using if or unless.

• If he does not carry out my orders, he will be sacked.
• Unless he carries out my orders, he will be sacked. (NOT Unless he does not carry out my orders, he will be sacked.)

We have already learned that unless means if not and hence it is wrong to use another not in clauses introduced by unless.

Exercise

Combine the following sentences using if or unless.

1. You must read the passage carefully. Otherwise you will not understand it.

2. She must buy a ticket. Otherwise she will not be allowed to watch the program.

3. He must stop smoking. Otherwise he will get cancer.

4. You must learn English. Otherwise you will not get a good job.

Answers

1. If you do not read the passage carefully, you will not understand it. / Unless you read the passage carefully, you will not understand it.

2. If she does not buy a ticket, she will not be allowed to watch the program. / Unless she buys a ticket, she will not be allowed to watch the program.

3. If he does not stop smoking, he will get cancer. / Unless he stops smoking, he will get cancer.

4. If you do not learn English, you will not get a good job. / Unless you learn English, you will not get a good job.