Sometimes, though not often, he had dreams, and they were more painful than the dreams of other boys.

有时，尽管不是经常，他会做梦，而且比其他孩子的梦更痛苦。

It is not often that you get such an opportunity.

你得到这样的机会，可不是常有的事。

It is not often that you get such an opportunity to be an exchange student.

你得到成为交换生这样的机会，可不是常有的事。

If you dream about some particular subject, it is not often that the dream is about that thing.

如果你梦到某个特定的主题，这并不是说梦就与那件事情有关。

The pilosus is a plant not often seen.

毛轴莎草是一种不太常见的植物。