noun
lowness; inferiority
Used to describe a low degree, value, or quality, often in contrast with 上 (じょう). Common in set phrases like 下の下.
この品質は下の下だ。
This quality is the lowest of the low.
noun
second volume (of two); third volume (of three)
Used in the context of multi-volume works, where 上 is the first volume, 中 is the middle (if three), and 下 is the last. Compare 上 (じょう) and 中 (ちゅう).
この小説は上下巻で、下巻が来月発売される。
This novel is in two volumes, and the second volume will be published next month.
上 (じょう) means 'first volume' or 'high quality', the opposite of 下 (げ) in both senses.
中 (ちゅう) is used for the middle volume in a three-volume set, between 上 and 下.
The reading げ is the on'yomi of 下, used in compounds and as a bound noun. The meaning 'lowness' is an extension of the spatial sense of 'below'.