频度副词的位置通常是在句子中系动词、助动词或情态动词之后，以及行为动词之前。1. 频度副词的定义：频度副词是用来表示动作发生频率的英语词汇。2. 常见频度副词包括：always、usually、often、sometimes、seldom和hardly等。3. 改写后的双语例句：

（1）在系动词之后：She is sometimes very busy.

改写：Sometimes, she is very busy.

（2）在助动词或情态动词之后：I will never forget this lesson.

改写：I will never forget this lesson.

（3）在实义动词之前：We often go there.

改写：Often, we go there.