Rey interacts with BB-8 vocally many times and appears to understand very complex topics within the language Droid Binary - such as the names of planets, coordinates, and short explanations about BB-8's mission secrecy.

It appears that Rey, who appears to have been living as a scavenger since her childhood, understands Binary.

Is there any in-universe (movie, novel, Disney accepted canon) explanation that would show when/where/why she learned this skill?

It isn't a widely known skill - Luke had C3PO translate for most of his earlier interactions, and then much of the communications between R2 and him occur in a cockpit with a display, though it's obvious he was able to pick up on the tone of the conversations R2 had and perhaps understand a little. Luke grew up on a desert planet with moisture evaporators and droids, but he obviously didn't understand the language at that time.

It seems like an odd thing for a young woman to have picked up on a planet where droids were apparently uncommon enough that they were routinely disassembled for parts and sold.

  • It isn’t widely-known because Luke didn’t know it? – Paul D. Waite Jan 12 '16 at 14:53
  • “Luke grew up on a dessert planet” — Like this? – Paul D. Waite Jan 12 '16 at 14:55
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    @PaulD.Waite I posted this an example of someone being around droids from youth and having to work with them not ever learning droid binary to strongly contrast against this situation where someone spent little to none of their youth/teen years around droids and yet knowing their language very well. In other words, she must have needed or desired to learn it for some reason, and it appears she wasn't in a environment where practice would be common or easy. She didn't sound rusty, as though she learned it prior to landing on the planet - it was easy and clear for her. – Adam Davis Jan 12 '16 at 14:56
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    @PaulD.Waite Few knew this, but the main export of Tatooine was puff pastry - and the seminal reason the Hutts exerted control. It wasn't their genetics alone that made them huge. – Adam Davis Jan 12 '16 at 14:59
  • Yeah, true true. – Paul D. Waite Jan 12 '16 at 15:40