常常的英文：
frequently
usually
often

参考例句：

He regularly neglects brushing his teeth before going to bed.
他常常忘记睡前刷牙。

Doctors used to bleed people when they were ill.
从前医生常常给病人放血.

Animals with rabies often froth at the mouth.
患狂犬病的动物常常口吐白沫.

Hurricanes periodically menace the Gulf Coast.
飓风常常威胁着墨西哥湾海岸。

hurricanes periodically menace the Gulf Coast
飓风常常威胁着墨西哥湾海岸。

Industrial effluent often causes a problem to people's health
工业废水常常危害人们的健康。

Net ball is a very common fault.
落网球是非常常见的失误。

Faultfinder:One who is given to petty criticism and constant complaint.
吹毛求疵者：爱挑毛病，常常抱怨的人。

Master of Science if often abbreviated to MS.
理科硕士常常缩写为MS.

Disaffection often leads to outright treason.
政治上的不满常常导致断然的背叛。

frequently是什么意思：
adv. 经常地

These faculae frequently are the forerunners of sunspot formation
这些光斑常常是形成太阳黑子的先兆。

To accustom by frequent repetition or prolonged exposure.
使……习惯由于经常重复或长时间接触而适应。

He is a frequent visitor to our house.
他是我们家的常客。

usually是什么意思：
adv. 通常，经常；一直，向来

Usually y is a function in math.
X is not a function in math.

Used as the usual style for a baron.
男爵用作男爵的常用称呼。

Mothers are usually gentle with their babies.
母亲对自己的婴儿总是很温柔。

often是什么意思：
adv. 时常，常常；往往，通常

They often gossiped.
They often gossiped.

Often the good suffer, and often the wicked prosper.
好人总是受气遭殃，坏人往往青云直上。

She often keeps a diary.
她常记日记。