Moving your head up and down, usually to show agreement, understanding, or greeting.
From Old English 'hnudda,' which referred to a sudden movement or thrust. The gesture became associated with agreement across many cultures independently.
Nodding to say 'yes' seems universal, but it's actually not—in Bulgaria, Greece, and Turkey, people shake their heads side-to-side to mean 'yes' and nod to mean 'no,' which causes hilarious confusion for travelers!
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