N-COUNT 下层;底层;深层特征;隐性特质 A substratum of something is a layer that lies under the surface of another layer, or a feature that is less obvious than other features. 下层;底层;深层特征;隐性特质 [formal]
...its deep substratum of chalk. [+ of]
深厚的白垩地层
His recreation of the city is credible, with a substratum of fact to bolster the fiction.