in·verse
                    
                                                                                                              
                                                                                                                                  (ˌ)in-ˈvərs  
                                                                                                                              
            ˈin-ˌvərs
                                                      
                                                          1
                    
                                          
              
          
                                                      : opposite in order, nature, or effect                                      
                
                    
2
                    
                                          
              
          
                                                      : being an inverse function                                      
              
                             
inverse sine
                         
                
                    2
                    
                                          
              
          
                                                      : a proposition or theorem formed by contradicting both the subject and predicate or both the hypothesis and conclusion of a given proposition or theorem                                      
              
                             
the inverse of "if A then B" is "if not-A then not-B"
                         
              
                                                         compare contrapositive                                      
                
                    3
                    
        a
    
          
                                          
              
          
                                                      : inverse function                                      
                
                                
            also                
          
                                                      : an operation (such as subtraction) that undoes the effect of another operation                                      
            
            
        b
    
          
                                          
              
          
                                                      : a set element that is related to another element in such a way that the result of applying a given binary operation to them is an identity element of the set                                      
                
                    
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  Merriam-Webster unabridged




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