What is the meaning of stratify?

verb

• Divide society into social classes or castes.
  • usage: "Income distribution often stratifies a society"
• Form layers or strata.
  • usage: "The rock stratifies"
• Develop different social levels, classes, or castes.
  • usage: "Society stratifies when the income gap widens"
• Form, arrange, or deposit in layers.
  • usage: "The fish are stratified in barrels"; "The rock was stratified by the force of the water"; "A statistician stratifies the list of names according to the addresses"
• Render fertile and preserve by placing between layers of earth or sand.
  • usage: "stratify seeds"