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top and bottom; up and down; high and low; above and below; upper and lower ends
upper and lower classes; ruler and ruled; the government and the people
「上下」 has other readings with different meanings.
この服は上下がセットで販売されている。
These clothes are sold as a set with top and bottom.
上下関係を大切にする文化がまだ残っている。
A culture that values hierarchical relationships still remains.
列車が上下線とも遅れが出ている。
Both the up and down train lines are delayed.