basis

basis (http://definr.com/basis)

     n 1: a relation that provides the foundation for something; "they
          were on a friendly footing" or "he worked on an interim
          basis" [syn: footing, ground]
     2: the fundamental assumptions underlying an explanation; "the
        whole argument rested on a basis of conjecture" [syn: base,
         foundation, fundament, groundwork, cornerstone]