[xià céng]
（指机构、组织） lower levels
go to lower-level units; go down to the grassroots level
深入下层
（指阶层） lower strata; sublayer
people of a lower social grade
下层社会的人们
cater for the humblest strata of the middle class
迎合中产阶级的最下层
Tramps are from the lowest stratum of society.
流浪汉来自社会最下层。
[生] substratum; substory