1. The first light of day
   - dawn, dawning, morning, aurora, first light, daybreak, break of the day, dayspring, sunrise, sunup, cockcrow

Type of: hour, time of day

• operation code
• Operation Desert Storm
• operational
• operational casualty
• operational cell
• operational damage
• operationalism
• operationalist
• operationally
• operations
• operations research
• operative
• operative field
• operatively
• operator
• operator gene
• opercular
• operculate
• operculated
• operculum
• operetta
• operon
• operose
• operoseness
• Opheodrys