stratum
noun [ C ] uk/ˈstrɑː.təm/ us/ˈstreɪt̬.əm/ strata /ˈstrɑː.tə/ us/ˈstreɪt̬.ə/
部分；层；阶层
one of the parts or layers into which something is separated
The report shows that drugs have penetrated every stratum of American society. 报告显示，毒品已经渗入美国社会的各个阶层。
geology specialized层;岩层;地层
a layer of rock, soil, or similar material
The cliffs are characterized by remarkable zigzagging strata of shale and sandstone. 这些悬崖的特征是它们由一层层清晰易辨的页岩、石灰岩和砂岩交错构成。