The document discusses the past unreal conditional. It explains that a conditional sentence has two parts: a condition and a result. For a past unreal conditional, the condition is in the past perfect tense and the result uses "would" plus the verb. Some examples are provided and analyzed. It is explained that for a past unreal conditional, the condition was not actually true in the past, so the result described did not occur either. The construction of past unreal conditional sentences is also covered, noting that the condition is always in the past perfect tense.