A "tornado outbreak" is often defined as six or more tornadoes produced by the same weather system within a day.
VOA: special.2010.05.11
Whatever the convention is within a system of differences, that's what makes the sign intelligible.
这些惯例存在于一个有差别的系统中,这就让符号变得有意义了。
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。
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