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Comment by zen_of_prog | Hacker News Reader

Concrete is made up of both cement (the CONtinuous part) and aggregate/stone (the disCRETE part), so cement vs concrete is kind of like broth vs soup, and concrete and stone like soup vs vegetables.

> So the main difference is that you can shape it without chiselling it.

I guess, yeah. Both are really good at withstanding compressive forces. Unlike Roman times, concrete today is usually reinforced with steel rebar, which gives it good tensile strength as well. This makes it useful for a lot of things that stone is not.

Disclaimer, take everything here with a grain of salt. Continuous-discrete is not the etymology of concrete. This might help too: https://youtu.be/UOHURuAf5iY

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Thanks. This was a helpful comment, especially the CONtinuous/disCRETE thing.

The " CONtinuous/disCRETE" might be useful as a mnemonic device, but you should be aware that there is no relationship between "concrete" and the "-tinuous/dis-" part.

"Con-" from "concrete" is indeed the same prefix as the "con-" from "continuous" and in both cases it means "together".

However, "-crete" from "concrete" is not the same suffix as the "-crete" from "discrete".

"-crete" from "concrete" means "grown" (it is the participle of the Latin verb "crescere", to grow), so "concrete" means "grown together".

"-crete" from "discrete" means "sifted" (it is the participle of the Latin verb "cernere", to pass through a sieve, to separate), so "discrete" means "sifted away", it comes from the same source as the verb "to discern".

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.

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.

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