1. the underlying support or foundation for an idea, argument, or process
2. the principal component or ingredient of something
3. the system or principles according to which an activity is carried on

Examples

• The theory lacks a solid scientific basis.
• What basis do you have for making that claim?
• Trust forms the basis of any good relationship.
• The sauce uses tomatoes as its basis.
• We meet on a weekly basis to discuss progress.
• The company operates on a profit-sharing basis.
• There is no basis for his accusations.