This document discusses the past perfect continuous tense in English grammar. It provides definitions and examples to explain the usage and meaning of this tense. Specifically, it states that the past perfect continuous tense is used to describe an action that was ongoing or progressing up until a specific point in the past. It then gives three main functions of this tense: 1) to describe an action that was ongoing in the past until a certain past time point, 2) in conditional sentences, and 3) in reported or indirect speech. The document also provides formulas to conjugate the past perfect continuous tense in positive, negative, and interrogative forms. Finally, it distinguishes the past perfect continuous tense from the present perfect continuous tense.