We music lovers mostly know what some of those notations like piano and fortissimo mean. Even things like Un poco meno mosso. But the Germans (of course) like to do it their own way, with things like sehr lebhaftig. Fortunately, David Pesetsky, a linguistics prof at MIT, has compiled a list of translations of the composer's markings in the score of Mahler's First. It certainly clears up a lot of things about Mahler. I mean, who knew it was all about spit valves?