English Grammar Explanations - Conditionals
esl.fis.edu/grammar/rules/cond.htmIf you had helped me, I would have helped you. If I had won the lottery, I would have bought a new car. If it had snowed yesterday, we would have gone skiing. Of course, it is possible to start conditional sentences with the main clause: I will buy a new car if I win the lottery. I would buy a new car if I won the lottery.