Finally, a definition of “paradigm” I can understand:

So let’s get clear: a paradigm is made out of units and rules. It says, “the part of the world I’m studying is made up of these entities, which can do these activities.”

In this way, doing science is a lot like reverse-engineering a board game. You have to figure out the units in play, like the tiles in Scrabble or the top hat in Monopoly. And then you have to figure out what those units can and can’t do: you can use your Scrabble tiles to spell “BUDDY” or “TREMBLE”, but not “GORFLBOP”. The top hat can be on Park Place, it can be on B&O Railroad, but it can never inside your left nostril, or else you’re not playing Monopoly anymore.

From Adam Mastroianni, and the rest of the article is even better.