mutism
noun
                                                                                                                            
                                                            mut·ism
                    
                                                                                                              
                                                                                                                                  ˈmyü-ˌti-zəm 
                                                      
                                                          
            
                                
              
          
                                                      : the condition of being unable to speak whether from physical, functional, or psychological cause                                      
                
                    
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  Merriam-Webster unabridged




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