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How does someone learn droid binary? It seems simple, but honestly, I don't see how anyone could (easily) learn how to understand droid binary. It seems to be just beeps and whistles. How do you say or understand words like that?
Of course, you don't really need to speak droid binary, just understand it, as droids understand most languages as far as I can tell.
P.S: You know the "Bad Feeling" running gag in all Star Wars films so far? Well, it isn't missing from The Last Jedi. Apparently, the line is said by BB-8 in droid binary.