PAST PERFECT TENSE KEY : Past perfect tense is used to express something happened completely before another activity in the past time.From the definition we can see that both activities happenned so close. Study this follows! Sandy had finished the assignment before the teacher came to the class. Sandy had finished the assignment = Past perfect tense The teacher came to the class = Simple Past tense Before = Conjunction which is used to describes both activities in the past time. In this case, the first activity which happened is /Sandy had finished the assignment/ and athe second activity is /The teacher came to the class/. In other words, Past perfect tense precedes the simple past tense. We use Simple past tense here is to describes the real events/activities in the past time and how past perfect tense is used. And, most of cases use past perfect tense together with simple past. It is the same as when Past Continuous is used in line with Simple Past Tense. Here's the formula of Past perfect tense: For examples: Take notice that auxilliary /had/ is used for all subjects (singular or plural, count- /uncountable noun, Ir-/regular noun). HOW TO BUILD A PAST PERFECT When we hear the Perfect word, we will straightly remember to all tenses which concerns to the word perfect, e.g. present perfect tensem past perfect tense, future perfect, past future perfect, present perfect coninuous tense, etc. Past perfect structure is built from the 'pastenate' auxilliary "have/has" to be /had/. This change causes the change in the usage. Here, The present or the past depends on the auxilliary. Keep learning happily!