1In mahjong, the area in front of each player where their discarded tiles are laid out in rows. The term comes from Chinese 河 ("river"), because the line of discards resembles a river. Read either as hō (from Chinese) or kawa. Players read opponents' 河 to infer what they are waiting for.
相手の河を見て、もう萬子は通ると判断した。
Looking at my opponent's discards, I figured the man-zu tiles would be safe to throw.
河に同じ筋の牌が並んでいると、待ち牌が読みやすい。
When the discards line up along the same suji, it's easier to read what your opponent is waiting for.
初心者のうちは、自分の手ばかり見て河を見落としがちだ。
Beginners tend to focus on their own hand and overlook the discard piles.