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The piano and the guitar are different in many ways, but they also have some similarities depending on how you play them.

Mechanically, sure, nothing transfers. Rhythm transfers pretty well. An ear for what sounds right would too.

If you're reading printed music, that transfers. A lot of guitar play comes from tabs though, which isn't really transferrable.

If you play chords on the piano and the guitar, and especially if you're thinking about chord progressions, that transfers. But you might play either instrument without a lot of chords.

Lead melody kinds of things can transfer a bit. Especially if you were thinking about how the notes in the melody fit with the chords, even if you didn't play the chords.

Even if you didn't think you were learning music fundamentals, you might have picked up something.