[MatteoFrigo]

Knuth's "Concrete Mathematics" book claims to be a blend of CONtinuous and disCRETE mathematics. Thus, Knuth is using the suffix "-crete" incorrectly as well.

If I were you, I would send an email to Knuth reporting the error. You may receive a reward check from Knuth himself, which will give you eternal bragging rights.

[adrian_b]

I believe that Knuth knew very well the true meanings of "concrete" and "discrete" and he has just made a word play exploiting the fact that the "-crete" suffixes in the 2 words are homonyms.

However, not all his readers have understood the pun.