I'm not certain it's meaningful, unless you are in the habit of giving your furniture personal names.

我不确定它有意义，除非你们热衷于,给你们的家具起名字。

麻省理工公开课 - 计算机科学及编程导论课程节选

Then again, if you are not certain of something you can say "I'm not sure."

同样的，如果你对于一件事没有把握，你可以说“I'm not sure.”

I'm sure 课堂 - SpeakingMax英语口语达人

I'm not 100% certain how that works.

它怎样运作我并不十分清楚。

耶鲁公开课 - 死亡课程节选

We have to not talk-- just talk about the good things in the life, but the good of life itself, and we have to notice that perhaps on certain views, for certain cases, it's not really the case that when I die I'm being deprived of a good life.

我们不但要看到-,生活中的美好事物，还要看到活着本身的好处，我们发现也许有某些观点，在某些情况下，情况则不完全是这样,即我死之后不会被剥夺美好的生活。

耶鲁公开课 - 死亡课程节选