How long? bao lâu after the verb

Bao lâu asks how long something lasts. It goes after the verb, where the length of time will go in the answer: Anh ở Việt Nam bao lâu? How long are you staying in Vietnam? Anh ở hai tuần. Two weeks.

You can put trong (for, within) in front, trong bao lâu, which sounds a little more careful. In everyday speech it's usually left out.

The answer is a number and a unit of time: mười phút, hai tiếng (two hours), ba ngày, một tháng. For a number of hours, say tiếng; hai giờ usually means two o'clock.

Four neighbors look alike. Bao lâu nữa asks how much longer until something happens, and often comes first: Bao lâu nữa thì xong? How much longer until it's done? Bao lâu rồi asks how long something has been going on, up to now: Em học tiếng Việt bao lâu rồi? Mất bao lâu asks how long a trip or a job takes: Đi Vũng Tàu mất bao lâu? And khi nào, or bao giờ, asks when, not how long.