layer vs upper mantle

layer and upper mantle both are nouns.

Word	Noun	Adjective	Verb	Adverb
layer	Yes	No	Yes	No
upper mantle	Yes	No	No	No

As nouns, upper mantle is a hyponym of layer; that is, upper mantle is a word with a more specific, narrower meaning than layer:

layer: a relatively thin sheetlike expanse or region lying over or under another
upper mantle: the upper part of the mantle

layer (noun)	upper mantle (noun)
thin structure composed of a single thickness of cells	the upper part of the mantle
a hen that lays eggs
single thickness of usually some homogeneous substance
an abstract place usually conceived as having depth
a relatively thin sheetlike expanse or region lying over or under another

layer (verb)	upper mantle (verb)
make or form a layer