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one
「一」 has other readings with different meanings.
いーを三枚集めて上がった。
I collected three 'one' tiles and won.
まだいーの牌が見えていない。
The 'one' tiles haven't appeared yet.
いーを捨てるか持つか迷ったけど結局捨てた。
I was torn between discarding and keeping the 'one' tile, but ended up discarding it.