How many问数量多少，而且接的是复数名词，how often问的是频率，多久做什么什么事情.举例来说，How many people are there in your family?你家有几口人，回答的时候直接说数字就可以了，Three，five之类的 often should I take this medicine ? Three times a day。
How many和how often是两个截然不同的短语，How many用来提问数量，后面跟可数名词的复数形式。如how many students are there in your school
How many books does he have?How often用于提问频率，多久一次。例如，how often do you visit your parents
Once a week.
