Not started
Duration leading up to a point in the past.
Why you specifically
Thì quá khứ hoàn thành tiếp diễn (past perfect continuous) dùng để nói về một hành động đã bắt đầu và đang diễn ra trong một khoảng thời gian trước một mốc khác ở quá khứ. Công thức là had been + V-ing. Trọng tâm của thì này là thời lượng và tính đang diễn ra trước một sự việc quá khứ khác, chứ không phải kết quả đã hoàn thành. Thường đi với các cụm như for, since, all morning, all day, before, when + mốc quá khứ. Ví dụ: She had been studying for three hours when the exam started. Câu này nhấn mạnh rằng việc học đã diễn ra liên tục trong 3 tiếng trước khi kỳ thi bắt đầu. Một ví dụ khác: I had been working all day, so I was tired. Nghĩa là tôi đã làm việc suốt cả ngày trước đó, nên tôi mệt. Người Việt học tiếng Anh hay dùng quá khứ đơn hoặc một cụm thời gian là đủ, nhưng trong tiếng Anh cần had been + V-ing để làm rõ hành động đã đang tiếp diễn trước một mốc quá khứ khác.
The rule
Past perfect continuous is used for an action that was already in progress before another point in the past. Its form is had been + verb-ing, and it often appears with time expressions such as for, since, all morning, or when/before + past event. The focus is on duration and background action, not on a completed result. Compare: She had been studying for three hours when the exam started. This means the studying was happening before the exam started and had continued for some time. In narratives, this tense often explains why something in the past happened, such as I had been working all day, so I was tired. In English, this is different from Vietnamese, where the same idea may be shown by a time phrase plus a simple past or present progressive-like expression; English still needs the past perfect continuous form to make the earlier ongoing timing clear.
The trap
She was studying for three hours when the exam started.
She had been studying for three hours when the exam started.
Use past perfect continuous for an action that was already in progress before another past event. Vietnamese often uses a simple past or a duration phrase, but English needs had been + verb-ing to show the earlier ongoing action.
They waited for the bus for a long time before it arrived.
They had been waiting for the bus for a long time before it arrived.
The action continued up to a point in the past, so had been waiting shows duration before another past event. The simple past waiting does not show that earlier background duration clearly enough.
I was working all morning, so I was tired when you called.
I had been working all morning, so I was tired when you called.
Past perfect continuous is common for the cause of a past result. The action was ongoing before the later past result.
She lived in Hanoi for two years before she moved to Da Nang.
She had been living in Hanoi for two years before she moved to Da Nang.
Use past perfect continuous for an action or situation that continued for a period up to a later past point. Vietnamese learners often overuse the simple past here.
Prove it
12 drills
You have not fought this one yet.
