ソウ 
() story in a building () stratum () social class () layer
            
そう (n,n-suf) (1) layer, seam, bed, stream, class, (2) (math) sheaf, (ctr) (3) storey (of a building), story, floor
そういがく (n) stratigraphy
そううん (n) stratus
そうか (n,vs,adj-no) (1) layering, stratification, (2) (math) sheafification
そうかんり (n) (comp) layer-management
そうぐん (n) (geol) group
そうじょがく (n) stratigraphy
そうじょう (n,adj-no) stratified
そうせきうん (n) stratocumulus
そうそう (n) facies
そうべつ (n,vs,adj-no) stratification, classification, (data) distribution
そうろう (n) tall building

Links: KanjiDic: EDict : Wikimedia
Etymologies: 中文字譜 : 説文解字