1. to arrange or organize things into groups based on shared characteristics
2. to designate information as secret or restricted
Usage: government/military context

Examples

• Scientists classify animals into different species based on their DNA.
• The library uses a system to classify books by subject.
• Please classify these documents according to their importance.
• The government decided to classify the military reports.
• Biologists classify organisms into kingdoms, phyla, and classes.
• The teacher asked students to classify the rocks by their mineral content.
• Intelligence agencies classify sensitive information to protect national security.