often后面一般是加动词的原形形式，表示一般现在时；后面也可以加动词的过去式形式，表示一般过去时。但是如果主语是第三人称的话，那么后面要用动词三单的形式。
1、加动词原形:How often do you brush your teeth?你多久刷一次牙？
2、加动词的过去式:People with the disease were often treated as social outcasts.患有这种疾病的人常被社会摈弃。
3、动词三单形式：A red sky at night often indicates fine weather the next day. 夜空呈红色往往预兆第二天天气晴朗。
often
一、含义
这个单词是一个形容副词，主要是表示：经常；往往；常常；时常；大多。
二、具体运用方法
1、The disease often goes/ remains undetected for many years.这种疾病经常潜伏多年而不被察觉。
2、I've often wondered what happened to him.我时常纳闷他出了什么事。
3、We should meet for lunch more often.我们应该更常一点相聚在一起吃午饭。
4、All too often the animals die through neglect.动物因缺乏照料而死亡的事司空见惯。
5、You've tried that trick once too often.你故伎重施，可这次再逃不脱了。
三、关于often的常用短语搭配
more often 更经常；更多的时候
sometimes often 有时经常
however often 但是往往
declare often 说明
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