Strata are the layers rock has been laid down in. Rock strata, exposed strata, strata of sandstone.
Each layer is younger than the one below unless something has turned them over, which is the principle geology is built on — and reading strata is how the age of the earth was first worked out. Strata is the plural of stratum, and stratas is wrong. Figuratively, strata means layers of society: the upper strata. Note stratified, stratigraphy.
1nounstrataThe layers rock has been laid down in.
“The cliff shows strata of red and grey rock.”
2nounsocietyLayers of society.
“The new school brought together children from all strata of society.”
Too few real examples of this word to estimate which sense is commonest.
strata is layers.
Latin stratum means something spread out, from sternere, to spread. Street, structure and stratosphere come from the same spreading.
From strata title.
Etymology from Wiktionary, CC BY-SA