strat ‧ i ‧ fi ‧ ca ‧ tion /ˌstrætəfəˈkeɪʃ ə n, ˌstrætɪfəˈkeɪʃ ə n/ BrE AmE noun [uncountable and countable]
1 . when society is divided into separate social classes:
The Indian caste system is an example of social stratification.
2 . the way in which earth, rocks etc form layers over time
—stratify /ˈstrætəfaɪ, ˈstrætɪfaɪ/ verb [intransitive and transitive]