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red dragon tile
winning hand with a pung (or kong) of red dragon tiles
「中」 has other readings with different meanings.
中が来たら上がれるのに。
If only the red dragon tile would come, I could win.
中を三枚集めて役にした。
I collected three red dragon tiles and made a winning hand.
相手が中を捨てたので鳴くことにした。
My opponent discarded the red dragon tile, so I decided to call it.