This is the 16772nd most frequent Russian word.
слой
Layer.
In this sentence, 'слой' refers to a physical layer, specifically a layer of chocolate.
На пироге виден толстый слой шоколада.
There is a thick layer of chocolate visible on the pie.
Here, 'слои' (plural of 'слой') denotes stratified sections of the atmosphere, indicating its structured composition.
Слои атмосферы изучаются учеными.
The layers of the atmosphere are studied by scientists.
In this context, 'слой' is used metaphorically to represent a segment or class within society.