1The top and bottom, or upper and lower parts, of something; used to describe position or orientation.
この箱は上下を逆さまにすると中身がこぼれます。
If you turn this box upside down, the contents will spill out.
説明書には図の上下を確認するよう書かれている。
The instructions say to check the top and bottom of the diagram.
棚の上下で置く場所を分けて整理した。
I organized things by dividing the shelf into upper and lower sections.
2Rising and falling, or fluctuating — said of quantities, states, or conditions that go up and down.
為替相場は一日の中でも大きく上下する。
Exchange rates fluctuate significantly even within a single day.
血圧が上下しやすい人は定期的な検査が必要だ。
People whose blood pressure fluctuates easily need regular checkups.
客の入りは天気によって上下する。
The number of customers goes up and down depending on the weather.
3Repeatedly going up and coming back down; moving back and forth between an upper and a lower place (e.g., floors).
荷物を運ぶために階段を何度も上下した。
I went up and down the stairs many times to carry the luggage.
エレベーターが故障して、社員は階段を上下するしかなかった。
The elevator broke down, so employees had no choice but to go up and down the stairs.
4Those in higher and lower positions within a society or organization; a hierarchical distinction such as ruler and ruled.
その時代は上下の区別が厳しく、身分を越えることは難しかった。
In that era, the distinction between upper and lower classes was strict, and it was difficult to cross social status.
会議では上下の立場に関わらず自由に発言してほしい。
In the meeting, I want everyone to speak freely regardless of their rank.
5The first and second volumes of a work published in two parts; the "upper" and "lower" volumes.
その歴史小説は上下に分かれていて、合わせて千ページ近くある。
That historical novel is split into two volumes and comes to nearly a thousand pages combined.
上下セットで買うと少し安くなる。
Buying the two volumes as a set makes it a little cheaper.
6The top and bottom pieces of an outfit (jacket and trousers/skirt, etc.); a matching two-piece set of clothing.
面接には上下がそろったスーツを着ていくつもりだ。
I plan to wear a matching suit (jacket and trousers) to the interview.
子供用の上下セットのパジャマを買った。
I bought a children's two-piece pajama set.
ジャージの上下をそろえて洗濯した。
I washed the matching top and bottom of the tracksuit together.