class structure vs stratum

class structure and stratum both are nouns.

Word	Noun	Adjective	Verb	Adverb
class structure	Yes	No	No	No
stratum	Yes	No	No	No

class structure (noun)	stratum (noun)
the organization of classes within a society	an abstract place usually conceived as having depth
	a subpopulation divided into a stratified sampling
	people having the same social, economic, or educational status
	one of several parallel layers of material arranged one on top of another (such as a layer of tissue or cells in an organism or a layer of sedimentary rock)