Substantial/səbˈstænʃl/ Definition 1 of 3Pro Tip 1/3Quantitative Measure Used for describing things that can be measured, often related to size or degree. The research had a substantial number of participants. Pro Tip 2/3Not Total 'Substantial' indicates something is large, but less than complete or total. A substantial part of the forest remains untouched. Pro Tip 3/3Emphasis Addition Used to add emphasis, making a statement stronger or more forceful. His findings were supported by substantial research.