An algorithm is a set of procedures that when followed accomplishes some task. It's not really like a sentence or a book, but it's closer to a paragraph I suppose.

DaleSpeak: Sorry, I didn't receive it, perhaps it was rejected by my Norton algorithm.

NormalTalk: Sorry, I didn't receive it. Perhaps it was filtered out by my anti-virus software.

Sometimes the same task can be accomplished by using different algorithms: e.g., sorting.

Ceci n'est pas un seing.