Me: Buenas noches, Esmeralda.
Her: Good night.
~5 seconds pass
Her: Wait... did you say "buenas noches"?
Her visual context said English, her brain recognized a valediction1 and she responded. And then she actually heard what I said. Things like this must make neuro-scientists giddy.
 I had to look that word up; while salutation was firmly embedded in my mind I had no single word associated with the closing part.