one of the parts or layers into which something is separated部分;层;阶层
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。
specialized geology a layer of rock, soil, or similar material层;岩层;地层
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。