1. The natural form, constitution, or essential nature of a person or thing; innate character or disposition.
Usage: formal; philosophical; from Greek philosophy
2. In ancient Greek philosophy, the fundamental principle or substance underlying all natural phenomena.
Usage: historical; philosophy

Examples

• The philosopher argued that physis, not custom, determines human behavior.
• Understanding one's physis is essential to living in accordance with nature.
• The Pre-Socratics sought to identify the primary physis from which all things arise.
• Her physis inclined her toward solitude and contemplation.
• Ancient thinkers debated whether water or air was the fundamental physis of the universe.