Conjunctions play a crucial role in expressing conditions within a sentence by linking clauses that indicate the relationship between actions, events, or conditions. Conjunctions such as “if,” “unless,” and “provided that” are known as conditional conjunctions, which introduce conditions that must be met for a particular result to occur.

1. “If”: This conjunction is used to present a condition that must be fulfilled for the main clause to happen. For example, “If it rains, we will stay home.” The action of staying home is dependent on the condition of rain.

2. “Unless”: It is used to express a negative condition or exception. For instance, “She will not go to the party unless her friend accompanies her.” In this case, the condition of her friend’s presence is necessary for her to go to the party.

3. “Provided that”: This conjunction is used to specify a condition that, if met, allows the main clause to occur as expected. For example, “You can borrow my car provided that you return it by tomorrow.” The condition of returning the car by tomorrow is essential for borrowing the car.

In summary, conjunctions like “if,” “unless,” and “provided that” help to establish a cause-and-effect relationship within sentences, showing the dependence of one action or event on a specific condition being fulfilled.