fair sex vs stratum

fair sex and stratum both are nouns.

Word	Noun	Adjective	Verb	Adverb
fair sex	Yes	No	No	No
stratum	Yes	No	No	No

As nouns, stratum is a hypernym of fair sex; that is, stratum is a word with a broader meaning than fair sex:

Other hypernyms of fair sex include class, social class, socio-economic class.

fair sex (noun)	stratum (noun)
women as a class	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)