The third conditional is used to express hypothetical situations from the past that can’t possibly come true as the opportunity has passed. Of the four conditionals, it is the only one that can’t possibly happen, and, that refers to past incidents. It is like a wish that can never materialize.
The third conditional is grammatically the most difficult to form of the four conditionals, as it uses the past perfect and the past participle. The past perfect is used to form the conditional clause and would have followed by the past participle is used the form the result clause, both of which are hypothetical situations. (The ‘would have’ in the result clause can be replaced by should have, could have or might have depending on what’s being expressed).
If clause (condition) Main clause (result)
If this thing had happened this thing would have happened.
If + subject + past perfect subject + would have + past participle
If I had studied harder, I would have been a doctor.
In a third conditional sentence, the clauses are interchangeable but pay close attention to where the comma goes. Only use a comma if the conditional clause comes first.
I would have been a doctor if I had studied harder.
If I had practiced more often, I would have been a much better player.
I would have been a much better player if I had practiced more often.
In the third conditional, question formation is also important to know.
Question word + would + subject + past perfect + if + subject + past participle..?
What would you have done if I hadn’t called?
Exercise 1: correct the errors in the following third conditional sentences. Elicit why they are mistakes, again bringing focus to the rules of the third conditional. CCQ throughout.
If I find out earlier, I will buy the tickets on time.
If I had saw him coming, I’d have move.
If I’d stay in college, I’d have be a teacher by now.
If I had chose two different numbers, I’d won the lottery.
I wouldn’t been so tired in class today if I’d went to bed earlier.
Exercise 2: print out and cut up a set of cards for each group and instruct them to match two clauses to make third conditional sentences.
As an extra activity, have each group work together to write the sentences accurately, focusing on the correct punctuation.
For higher level students or groups that finish quickly, have them write the other possible way each sentence could be written.
Exercise 3: Class survey – this part of the lesson focuses on forming questions and giving answers in the third conditional.
Student A: What would you have done if you had slept-in this morning?
Student B: If I had slept-in this morning, I would have skipped class today.
Step 1: Elicit from students how to form the questions correctly, making clear that we still use the past perfect in the conditional clause and ‘would + subject + have’ plus the past participle in the result clause.
Step 2: Give each student a survey worksheet and have them write the questions in full, using the information given. (Check for accuracy)
Step 3: Have students walk around the class asking their classmates the questions. If there are enough students, encourage them to only ask one question per classmate.
Step 4: When the survey is finished, elicit how to report the answer using the third person. If students are higher level, encourage them to use reported speech phrases, such as, “Karl said, if he had slept-in this morning, he would have skipped class today”.