What ia an Algorithm? From where this word originated? What criteria an algoritm must satisfy?

An explicit step-by-step procedure for producing a solution to a given problem. Specifically, a mathematical equation typically executed using a computer program (or set of programs) that is designed to systematically solve a certain kind of problem. For example, in the field of meteorology, WSR-88D radars (NEXRAD) employ algorithms to analyze radar data and automatically determine storm motion, probability of hail, accumulated rainfall, and several other parameters.

* Originates from "algorism" with its ancient meaning, i.e., the process of doing arithmetic using Arabic numerals

Basically the best way I can describe it, and I'm sure there are bigger geeks out there than me, but an algorithm the word was originated from the greek language, maybe even latin roots.

The dictionary give this definition:

a procedure for solving a mathematical problem (as of finding the greatest common divisor) in a finite number of steps that frequently involves repetition of an operation; broadly : a step-by-step procedure for solving a problem or accomplishing some end especially by a computer