Metamath Proof Explorer
		
		
		
		Description:  A monoid is a semigroup with an identity element.  (Contributed by FL, 2-Nov-2009)  (New usage is discouraged.)
		
			
				
					|  |  | Ref | Expression | 
				
					|  | Assertion | df-mndo |  | 
			
		
		
			
				Detailed syntax breakdown
				
					
						| Step | Hyp | Ref | Expression | 
						
							| 0 |  | cmndo |  | 
						
							| 1 |  | csem |  | 
						
							| 2 |  | cexid |  | 
						
							| 3 | 1 2 | cin |  | 
						
							| 4 | 0 3 | wceq |  |