TOEIC Grammar Basics - The 3rd Conditional
What is the 3rd conditional in English?The second conditional form is used to express something that is impossible. Like all conditional forms, it contains an "if" clause and a "then" clause.
For example, "If I had invested money in Apple, (then) I would have been able to retire today." Meaning, I did not invest in Apple when the company was small, so I cannot retire today (impossible).
The "if" clause uses the past perfect; while the "then" clause uses "would + present perfect".
"If she had found her key, she would not have had to call the locksmith." Meaning, she misplaced her key somewhere and could not open the door (impossible), so she called the expert to let her in.
A very common usage of the 3rd conditional is the expression, "If I had known".
"If I had known, I could have helped you with your work." Meaning, if I had known that you needed help, then I could have been available to help you. But right now this is impossible
"If I had had another ticket, I could have taken you with me to the show."
Notice that the word "could" replaces the word "would". It is possible to use any past tense modal - although the most commonly used is "would". Also, the word "then" is optional in conditional sentences. We at Scott's English Success recommend that you write it in your formal writing, though.