London may be famous for its red double-decker buses, but it is the underground system, parts of it more than a hundred years old, that is especially vulnerable.

VOA: standard.2010.04.01

It says finally it came to place, according to this concocted system, and I've underlined in red, very many undiscovered members.

它说，最终它会找的位置的，根据这个调和的系统，我标了红色的下划线，有很多未被发现的成分。

麻省理工公开课 - 固态化学导论课程节选

The red light is intelligible, in other words, within that semiotic system.

红灯在这样的语境里，就有了它的意义。

耶鲁公开课 - 文学理论导论课程节选