/ ˈstrɑːtəm; NAmE ˈstreɪtəm/ noun ( pl. strata / -tə; NAmE /)
1.
( geology ) a layer or set of layers of rock, earth, etc.
2.
( formal ) a class in a society :
people from all social strata
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WORD ORIGIN
late 16th cent. (in the sense layer or coat of a substance ): modern Latin , from Latin , literally something spread or laid down , neuter past participle of sternere strew.