Dictionaries define blindness as "being without the sense of sign, " but there are many degrees of blindness.

字典定义失明为“没有视觉”，但是失明实际分为很多级别。我们把这个矩阵的秩定义为它所包含的线性无关行的数目。

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The reason is that the number of students refusing to state their race has jumped from 5.1% of the freshman class to 14.3%, a heartening sign that the doctrine of race blindness is at least catching on among the young.

ECONOMIST: Californian higher education