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1. A relation that provides the foundation for something
   "he worked on an interim basis"
   - footing, ground
    
2. The fundamental assumptions from which something is begun or developed or calculated or explained
   "the whole argument rested on a basis of conjecture"
   - base, foundation, fundament, groundwork, cornerstone
    
3. The most important or necessary part of something
   "the basis of this drink is orange juice"
   - base

Type of: assumption, component, component part, constituent, foundation, part, portion, supposal, supposition

Part of: explanation

Encyclopedia: Basis