层  層 
- to pile on top of one another
 - layer; stratum
 - floor (of a building); story
 - (math.) sheaf
 - classifier for layers
 
Examples
玩具部門在第五層。
大楼有20层。
平流層的臭氧會吸收紫外線。
Info
- Wiktionary: 层
 - MDBG: 层
 - Examples with 层 on Tatoeba
 - Percentile: 93 (higher is more common)
 - Tags: classifierHSK3