What is the formula of past perfect tense?

Related questions

1. Why there is no passive voice of future continuous tense?
2. What is a present active participle?
3. What is past perfect passive?
4. What is present perfect passive?
5. What is past simple passive?
6. What is an example of a passive sentence?
7. What is present simple passive?
8. What is done Cannot be undone voice change?
9. Do you know me change into passive voice?
10. What is passive and active exercise?

Tags

1. #subject
2. #perfect
3. #change
4. #matter
5. #plural
6. #doesn
7. #tense
8. #singular
9. #participle
10. #formula