|a plural of stratum|
|usage Strata is sometimes wrongly used as a singular noun: this stratum (not strata) of society is often disregarded|
stratum stra·tum (strā'təm, strāt'əm)
n. pl. stra·tums or stra·ta (-tə)
A horizontal layer of material, especially one of several parallel layers arranged one on top of another.
Any of the layers of differentiated tissue forming an anatomical structure.