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，和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。
例句
He often wore a baseball cap.
他经常戴顶棒球帽。
That doesn\'t happen very often.
那不常发生。
These fish are often eaten raw.
这些鱼常常生吃。
Disease often goes with poverty.
疾病与贫穷常常相伴而生。
