usually/ sometimes/always/often等词在英文中被称为“频度副词”,是用来表示动作频率的,但程度上有别.常见频度副词按频率大小排列如下：always(100%)>usually(80%)>often(60%)>sometimes(40%)>seldom(20%)>never(0%)◆频度副词在句中习惯上位于be动词、助动词等之后,行为动词之前.1.在be动词之后.如：She is sometimes very busy.她有时很忙.2.在第一个助动词或情态动词之后.如：I will never forget this lesson.我将永远忘不了这一课.3.在实义动词之前.如：We often go there.我们常去那儿.◆sometimes也可放在句首、句中或句末,often也可放在句末(一般不放在句首).如：Sometimes she writes to me.=She writes to me sometimes.她有时候给我写信.She writes to me often.她经常给我写信.◆如果有两个助动词,频度副词通常放在第一个助动词后面.如：We have never been invited to one of their parties.他们聚会,一次也没邀请过我们.She must sometimes have wanted to run away.她有时候一定想到过要逃走.
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