1. Tested and proved useful or correct
   - tested, tried

See also: proved, proven

• protozoal infection
• protozoan
• protozoic
• protozoological
• protozoologist
• protozoology
• protozoon
• protract
• protracted
• protractedly
• protractible
• protractile
• protraction
• protractive
• protractor
• protriptyline
• Protropin
• protrude
• protruding
• protrusible
• protrusile
• protrusion
• protrusive
• protuberance
• protuberant