an angle equal to 180°. Often called a line.
                                                            
                                                     
                        
                                                
                        
                        
                        
                                                
                        
                        
                            an angle whose measure is exactly 18.
                                                            
                                                     
                        
                                                
                        
                        
                            An angle with a measure of 180º.
                                                            
                                                     
                        
                                                
                        
                        
                            an angle whose initial and terminal sides form a straight line, its measure being 180° (or radians)
                                                            
                                                     
                        
                                                
                        
                        
                            An angle whose measure is 180°.
                                                            
                                                     
                        
                                                
                        
                        
                            A straight angle has a value of 180º. Two rays in opposite directions from their common endpoint form this angle.