经常, 再三
How often does the train run?
这火车多久一班?
【说明】此词一般用于动词之前, be 和助动词之后, 有时也用于句末以加强语气.
（1）often放在be动词后.
He is often late for school.
他经常上学迟到.
（2）often放在实义动词前.
He often goes to school by bike.
他常骑自行车上学.
（3）often与very或quite连用表示强调时,既可放句中,也可放句首或句末.
My father very often goes to Beijing on business.
Very often my father goes to Beijing on business.
My father goes to Beijing on business very often.
我父亲经常去北京出差.
习惯用语
as often as 每当
as often as not (=more often than not) 多次, 屡次, 往往
every so often 偶尔, 有时
once too often 又一次, 再一次, 次数太多
often and often 屡次三番, 经常
always, often, usually, frequently, repeatedly, regularly
这些副词均表示频度.
always: 总是,永远.语气最强,指在一切时候,没有例外.
often: 经常,语气弱于always,侧重动作发生的次数具有经常性,具体时间意味不强.
usually: 通常,通例地,指习惯性动作,频度仅次于always,较often大,偶尔有间隔.
frequently: 时常,经常,与often同义,可通用,但较正式,强调次数频繁.
repeatedly: 屡次,强调次数多,但反复的频率不一定均匀.
regularly: 用于修饰经常而有规律性的动作.
主语是复数形式，often后面动词用原型。主语是第三人称，often后用动词三单。often是频率副词，sometimes、always、never、frequently等一样表示习惯性。后接动词原形用于一般现在时。后接动词过去式用于一般过去时。
关于often的详细用法：
1.often通常和一般现在时态连用,所以不会用-ing形式.置于用现三单形式还是原形,这取决用主语,如果主语是单数第三人称,那就用现三单形式,其他情况下用原形
2.often后用动词一般使用一般现在时态。often前的主语是复数形式，后面的动词使用原型；often前的主语是三单形式，后面的动词变成相应的三单形式。
当often前面的主语是I或者We 时，后面的动词为动词原形。
例子：We often go to work（动词原形） by bus.我们经常乘公交去上班。
3.often后用动词一般使用一般现在时态，后面的动词根据主语的形式而发生变化。当主语是三单时，后面是动词的三单形式。
当often前面的主语是I 时，后面的动词为动词原形。如果often前面的主语是三单形式时，后面的动词也同样是三单形式。如果often前面的主语是复数形式，那么后面的动词就是动词原形。
often不是情态动词。情态动词后面要接动词原形。情态动词有:can may must should could 等。often是个频度副词，和一般现在时态连用，通常表示经常发生的动作。often的位置：表示“经常”，通常放在行为动词之前，特殊动词（助动词、情态动词以及动词be）之后。
often的用法
often的用法：一般用于动词之前, be 和助动词之后, 有时也用于句末以加强语气。
1.often放在be动词后。
He is often late for school.
他经常上学迟到。
2.often放在实义动词前。
He often goes to school by bike.
他常骑自行车上学。
3.often与very或quite连用表示强调时，既可放句中，也可放句首或句末。
My father very often goes to Beijing on business.
Very often my father goes to Beijing on business.
My father goes to Beijing on business very often.
我父亲经常去北京出差。
often的短语every so often
有时,偶尔 sometime
Every so often, she takes a weekend in London.她有时在伦敦过周末。
as often as not
1.经常在通常情况下
其实我有两个家，因为我常去她家里。
I had two homes really, because as often as not I was down at her house.
more often than not
1.往往，多半
食物很少，他们经常挨饿。
food is scarce and more often than not they go hungry.
