- how long 指多長...
- how long 指多長時間,用來對一段時間（如 for three days, for four weeks）提問
How long did he stay here? -- For one day.
他在這裏待了多長時間。—— 一天
How long do you think you'll be gone?
你認爲你會離開多久？
How long have you known her? -- For four years.
你認識她多久了？—— 4 年了。
- 用來提問具體物體的長度
How long is this room?
這間屋子有多長？
How long is the board?
這條木板有多長？