英语的否定有明暗之分，暗含否定缺乏明显的否定标志，因而当它通过一些特定的句式来表现时，对它的理解与翻译就存在一定的难度。

In English, negation can be realized by sentences with or without negative marks. Those sentences with no negative marks may cause some difficulties in being understood as well as translated.

youdao

这样就产生了档次之分。棕榈蜡收获时，根据颜色，纯度，以及生长地域进行分级。

That brings us to grading. carnauba is harvested and then graded according to color, purity, and where it was grown.

youdao

关联规则就数据项之间的相关性来说，可以有正负关联规则之分。

On the relevance of data, association rules have positive or negative association rules.

youdao

And I'll also remind you, and we're going to see this in the next example, we talked about looking at the worst case behavior. In these cases there's no best case worst case, it's just doing one computation.

我还要提醒大家的就是，我们也会在下一个例子里发现者一点，我们谈到了要去考虑最坏的情况,在下面这些例子里,没有好情况坏情况之分，就只是一次运算。

麻省理工公开课 - 计算机科学及编程导论课程节选