social class vs stratum

social class and stratum both are nouns.

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

As nouns, social class and stratum are synonyms defined as:

social class and stratum: people having the same social, economic, or educational status

Other synonyms of social class include class, socio-economic class.

social class (noun)	stratum (noun)
people having the same social, economic, or educational status	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)