It is often used in words to indicate a quantity of something, such as:
* Polyglot: A person who knows and is able to use several languages.
* Polytheism: The belief in or worship of more than one god.
* Polygon: A closed plane figure with many sides and angles.
* Polygraph: A lie detector machine that measures multiple physiological responses.
So, whenever you see the word "poly" in a word, you can generally assume it relates to the idea of multiplicity or abundance.