1. groups or sets of five things
Usage: formal; technical
2. periods of five days
Usage: meteorology; technical

Examples

• The data was organized into pentads for easier analysis.
• Each pentad contained five related elements.
• The meteorologist studied temperature changes over successive pentads.
• The ancient calendar was divided into pentads rather than weeks.
• Scientists grouped the specimens into pentads based on their characteristics.
• The research covered twelve pentads of observation.