how long和how often的區(qū)別在于中文含義不同、用法不同。how long意為“多長時間”，主要用來對for加一段時間和長度提問；how often意為“每隔多久”，主要用來對頻率副詞或者狀語提問。
一、how long的中文釋義及用法介紹
how long意為多長時間，主要用來對一段時間(如three days, four weeks 等)提問的。
例句：How long ago was it?
這是多久前的事了?
How long have you been employed at this job?
你受雇做這個工作有多久了？
How long have you lived around here?
你住在這一帶有多長時間了？
You sneak a look at your watch to see how long you've got to wait.
你偷偷地望一眼手表，看看要等多長時間。
How long he'll be able to do so is a moot point.
不知道他還能這樣做多久。
How long will it take you to knit up this pattern?
你織完這個花樣要多長時間？
二、how often的中文釋義及用法介紹
how often意為每隔多久，主要用來對頻率副詞或狀語(如once a week等)提問的。
例句：How often does he come here? —Once a month.
他(每隔)多久來一次?每月一次。
How often do you go to the cinema?—once a week.
你多長時間去看一次電影？—一周一次。
How often do you actually get a gift you really need?
你會多久收到一個你確實需要的禮物？
How often do you water these trees?
你多久給這些樹澆一次水？
