how often 指每隔多久，主要用来对频度副词或状语(如：once a week, three times a month 等)提问。
具体用法
01.主要用来问频率的。比如：How often do you take exercises?你多久锻炼一次？twice a week.我一周锻炼两次.I take exercises every day，我每天都锻炼身体.
02.用来提问某动作或者状态发生的频率，指的是“一段时间内发生了几次活动”。How often do your parents let you to watch TV.你的父母多久让你看一次电视？
03.注意和how soon,how long的区别，how soon主要是对“多快，多久”提问？How soon will you come back？how long是就 "一段时间"提问的，how long have you lived here?
04.注意和how far的区别，how far主要是就"距离"提问的，how far can you throw the ball?
相似短语
how often 多久；多常；多久一次
as often as not 经常,时常,往往
as often as 每当,每次
often and often 经常,常常,每每,屡次三番
and how 的确,当然,无疑
How To adj.基本知识的
How to 操作方式
how to adj.基本知识的
how was it 怎么样
as is often the case 这是常有的事
