1. to make or become deeper in physical depth
2. to make or become more intense, serious, or profound
3. to make or become darker in color

Examples

• The workers will deepen the harbor to allow larger ships to dock.
• Her voice began to deepen as she grew older.
• The crisis will only deepen if we don’t act quickly.
• Their friendship deepened over the years.
• The sunset deepened the red color of the canyon walls.
• His understanding of the subject deepened through practice.
• The recession continued to deepen throughout the year.