base layer; substratum; binder course
Technical term used in geology, construction, and linguistics for a foundational layer or underlying stratum.
道路の基層にはアスファルトが使われている。
Asphalt is used for the base layer of the road.
この地域の基層は古い岩盤でできている。
The substratum of this region is made of old bedrock.
Compound of 基 (ki, 'base, foundation') and 層 (sō, 'layer, stratum'). The exact historical derivation is uncertain, but the word follows standard Sino-Japanese compounding patterns.