stratum

名词 stratum:

1. one of several parallel layers of material arranged one on top of another (such as a layer of tissue or cells in an organism or a layer of sedimentary rock)
2. an abstract place usually conceived as having depth
   同义词：level, layer

1. A sharp ridge with steeply sloping sides, produced by erosion of the broken edges of highly tilted strata.
   豚脊丘，陡峻的山脊由于对高斜层破碎山背的侵蚀而形成的陡峭的山背
2. A problem that cuts across all strata of society
   一个影响到一切社会阶层的问题。