nm. stratus, low-altitude cloud formation consisting of a gray horizontal layer with a relatively flat bottom; layer, stratum

n. bedding; layer, stratum

(n.) = stratum [strata, -pl.].
Ex: However, amongst this stratum of the population, library users demonstrated greater residential stability.
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* estrato sedimentario = rock stratum.
* estrato social = social stratum.
* provenir de todos los estratos sociales = come from all + walks of life.