カイ 
きざはし 
() storey () stairs () counter for storeys of a building
       
かい (n,n-suf) (1) storey, story, floor, (n) (2) stairs, (n,n-suf) (3) stage (in chronostratigraphy), (ctr) (4) counter for storeys and floors of a building
かいきゅう (n) class, rank, grade
かいそう (n) class, level, stratum, layer, hierarchy
かいだん (n) stairs, stairway, staircase

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