Explanatory means something that explains or helps make something clear. An explanatory note at the bottom of a page tells you what a confusing word means. An explanatory diagram shows how a machine works. When your teacher writes an explanatory comment on your essay, she's clarifying why you lost points or what you did well.

Something explanatory answers questions like “why?” or “how?” Think of the difference between a simple list of instructions and instructions with explanatory details: the first just tells you what to do, while the second helps you understand why you're doing it that way.

You'll often see this word in phrases like “self-explanatory,” which describes something so clear it needs no additional explanation. If your friend shows you a game and says “it's self-explanatory,” they mean the rules are obvious once you start playing. Scientists write explanatory papers to help others understand their discoveries. Museums use explanatory plaques to tell you about the exhibits. Anytime someone creates something to help others understand, they're being explanatory.