two
「二」 has other readings with different meanings.
two; 2
りゃんを二枚捨てた。
I discarded two 'two' tiles.
りゃんが三つ揃えば役になる。
If you collect three 'two' tiles, it becomes a winning hand.
りゃんを鳴いて手を進めることにした。
I decided to call the 'two' tile and advance my hand.