adjective. 
                    Someone or something that many people know about, renowned, famous.
                  
                
                  
                    verb. 
                    Past participle of know
                  
                
                  
                    noun. 
                    In algebra, a variable or constant whose value is already determined.
                  
                
                  
                    noun. 
                    Any fact or situation which is well-researched or familiar.