verbs in conditional sentences

A conditional sentence contains a dependent clause that expresses a condition; that condition must be fulfilled in order for the result expressed in the main clause to take place. A conditional clause usually begins with the conjunction if.

Since the tenses in conditional sentences differ widely depending on the situation, writers are often confused about what tense to choose. The choice of tense in English depends on two factors: (a) the degree of reality, probability or possibility attached to the condition; and (b) the time of the action.

Follow the basic guidelines below to help you choose the correct tense in a conditional sentence.

A. Real situations

Real situations are situations that are actual or possible. They include situations that are known to happen as a general rule; situations that are known to have happened in the past; situations that could possibly happen in the future; or situations that could possibly have happened in the past.

• General truth: if + present + present
  • If the temperature reaches 100 °C, water boils.
  • If you throw a ball up, gravity causes it to fall back down.
  • If it is sunny, the children play outside.
• Future possibility: if + present + future
  • If I get a raise, I will take you out to dinner.
  • If it rains tomorrow, the children will play inside.
• Actual past situation with present result: if + past + present
  • If I was too blunt, I apologize.
• Actual past situation with past result: if + past + past
  • If Al made a snack, he always cleaned the kitchen.
• Possible past situation with past result: if + past + would*
  • If Sarah was in the garden, she wouldn’t have heard the phone.
    [We don’t know whether she was in the garden, but it’s possible.]
• Possible past situation with future result: if + present perfect + future
  • If any trees have blown down, we’ll need to clear the road.
    [We don’t know if any trees have blown down, but it’s possible.]

B. Unreal situations

• Unlikely, imaginary or impossible situation (present or future): if + simple past + would*
  • If Ed decided to ski next winter, he would buy new boots.
    [but he probably won’t decide to ski]
  • If you got up earlier, you’d be on time.
    [but you probably won’t get up earlier]
  • If Pia had the money, she would take a cruise.
    [but she doesn’t have it; she can only dream]
  • If wishes were horses, beggars would ride.
    [but that’s impossible]

  Note: In this type of clause, for the verb be, Canadians prefer the subjunctive were with all subjects:

  • If I were (not was) invited, I would go.
  • If Gayle were (not was) here, Lena would be so pleased.

• Past situation that did not happen: if + had + would* have
  • If Sue had played, we would have won. [but she didn’t]
  • If Karl had insisted, I would have gone with him. [but he didn’t]

  Note: Do not use would have in the if clause.

  • If you had (not would have) asked me, I would have helped.

*Although would is the most commonly used conditional verb, other conditional verbs such as could or might can also be used in place of would in conditional sentences, depending on the writer’s meaning: e.g. If Sarah was in the garden, she couldn’t have heard the phone. If Sue had played, we might have won. If you had asked me, I could have helped.