Stratum
Pronunciation : Stra"tum, n.; pl. E. Stratums
Part of Speech : L.
Etymology : [L., from sternere, stratum, to spread; akin to Gr. Strew, and cf. Consternation, Estrade, Prostrate, Stratus, Street.]
Definition : 1. (Geol.)
Defn: A bed of earth or rock of one kind, formed by natural causes, and consisting usually of a series of layers, which form a rock as it lies between beds of other kinds. Also used figuratively.
2. A bed or layer artificially made; a course.
Strata. The latter is more common.
Source : Webster's Unabridged Dictionary, 1913