Explain the concept of 'unless' in conditional clauses and provide examples.

The concept of 'unless' in conditional clauses is used to express a condition that must be met in order for a certain result to occur. It is often used to convey a negative condition or to express something that is unlikely to happen. 'Unless' is typically used in the same way as 'if not' or 'except if'.

When 'unless' is used in a conditional clause, it means that if the condition stated after 'unless' is not fulfilled, the result mentioned in the main clause will occur. In other words, the main clause will only happen if the condition is not true.

Here are some examples to illustrate the use of 'unless' in conditional clauses:

1. Unless you study hard, you will not pass the exam.
- This sentence means that if you do not study hard, you will not pass the exam. The condition is not studying hard, and the result is failing the exam.

2. I won't go to the party unless my friends invite me.
- This sentence implies that the speaker will only go to the party if their friends invite them. If the friends do not extend an invitation, the speaker will not attend the party.

3. Unless it stops raining, we won't be able to go for a walk.
- This sentence indicates that the walk will only happen if the rain stops. If the rain continues, the walk will not take place.

4. Unless you apologize, I won't forgive you.
- In this example, the speaker will only forgive the person if they apologize. If no apology is offered, forgiveness will not be granted.

5. Unless you hurry, we will miss the train.
- This sentence means that if you do not hurry, we will not catch the train. The condition is not hurrying, and the result is missing the train.

In all of these examples, the main clause will only occur if the condition stated after 'unless' is not fulfilled. 'Unless' introduces a negative condition that must be avoided or changed in order to achieve the desired result.