• 階層かいそう — hierarchy; stratum
• 高層こうそう — high-rise; upper level
• 地層ちそう — geological layer
• 層状そうじょう — layered structure
• 断層だんそう — geological fault
• 深層しんそう — deep layer

The kanji 層 conveys stacked structure — things composed of multiple levels or layers. It’s used for floors of buildings, rock strata, cloud types, and even social or technical groupings.

Modern usage is common in architecture (高層ビル — high-rise building) and Earth sciences (地層 — rock layers).