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jaw; chin
barb (of a fishhook)
彼は頤に手を当てて考え込んでいた。
He was deep in thought with his hand on his chin.
転んだ拍子に頤を強く打ってしまった。
I hit my chin hard when I fell.
頤のラインが引き締まると顔全体が若く見える。
When the jawline is firm, the whole face looks younger.