Yale University is a non-profit corporation; the price of a share in Yale University is undefined-- it's zero over zero.

耶鲁大学可以看作是个非盈利组织,它的股价无法定义,是零除以零

耶鲁公开课 - 金融市场课程节选

Undefined reference, what was the solution last time?

未定义的引用，上次我们是怎么解决的呢？

哈佛公开课 - 计算机科学课程节选

But the take away for now is that if you don't clue -lcs50, -- you get some mention -- some error message -- about "undefined symbol," and that should be your clue that, "Oh it's undefined in that I haven't told the compiler that I want to link in these zeros and ones."

但现在如果你删除“-lcs50“,你们会得到一些提示--一些错误信息-,像“未定义的符号“，这可以为你提过线索，“这个没有被定义，我没有告诉编译器,把想把这个与“1“和“0“建立连接，“

哈佛公开课 - 计算机科学课程节选