stratum [ˈstreɪtəm]

例句:

• It was an enormous task that affected every stratum of society.
  这是一项影响到社会各阶层的重大工作。
  
• An aquifer is a water - bearing rock stratum such as sandstone and chalk.
  地下蓄水层是一些有水的岩石层,如沙岩和白垩岩.
  
• Such inequalities are found in every stratum.
  这类不公平的现象存在于社会的每一个阶层.
  
• So you have fully formed land animals in wrong evolutionary stratum.
  来自SA
• You might comb a rock stratum for weeks and not find a single fossil.
  来自SA
• An archaeologist finds a stratum of earth and stones and mortar, mixed with potsherds and coins.
  来自R. G. Collingwood