Geology and mining

The seventeenth entry is os estratos, and the Portuguese plural costs nothing: o estrato takes an -s and the job is done. English borrowed the word from Latin and borrowed the plural with it, so the pair is « a stratum » against « the strata », and the -s never appears. That matters: the field uses both forms. « The strata dip towards the sea » takes a plural verb; « this stratum is barren » takes a singular one. The commonest slip is « a strata », and the next is « stratas », which piles a second plural on the first. A geologist reads either as a sign of a writer who has not handled the material. It is worth storing because three famous words went the other way. « Data », « media » and « agenda » were Latin plurals too, and English has turned all three into singular mass nouns, so that « the data is clear » now passes. « Stratum » resisted, because here the counting is real: one can point at a single layer and then at forty. This is no rule about borrowings. It is a fact about this one.