下層(かそう)

下層(かそう) refers to the bottom level of any layered structure, whether physical or social. Composed of 下(か) (lower) + 層(そう) (layer, stratum). Can also function as a の-adjective.

Layer hierarchy

• 上層(じょうそう): upper layer/class
• 中層(ちゅうそう): middle layer
• 下層(かそう): lower layer/class

Common collocations

• 下層(かそう)階級(かいきゅう): lower class
• 大気(たいき)の下層(かそう): lower atmosphere
• 下層(かそう)土壌(どじょう): subsoil
• 社会(しゃかい)の下層(かそう): lower stratum of society

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A formal, academic word. Used in scientific writing (geology, meteorology) and social commentary. In everyday speech, 下(した)の方(ほう) is more common for physical layers.