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Origin of the Notation for Slope

Asked by Jessica, Marquette Senior High School on Friday Mar 22, 1996:
In the formula y=mx+b, why is m used for the slope? What does it stand for?
This question still has us stumped! Why and when did it become customary to use the letter m for slope?

If anybody knows the answer, please post a follow-up message using the form below. Here are a few comments that have been posted so far:

Follow-up comment by Dolores Greenberg (High School Librarian), La Habra High School:

I have a math teacher who has posed the question about the notation "M" for slope. I have hunted everywhere without success except to find that slope stands for "M"aximum rate of change of the function. Could this be the "M"?
It's possible, although I doubt it because slope is not really anything to do with "maximum" rate of change of a function, rather, just plain old rate of change.

However, I haven't been able to come up with anything more conclusive myself. It is most likely from some Latin word, but I am not sure which; another possibility is that it may be from the French montrer for "to climb". I'm still trying to find out something more definitive, and I'll keep you all posted!

Follow-up comment by Dolores Greenberg (High School Librarian), La Habra High School:

We are still working on it at this end. Our ideas to date: montagne Fr. for mountain, Magnitude method from siting artillery, related to M in the Greek alphabet somehow.
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