Difference between single equation and simultaneous equation models:

From the discussion so  far, we understand that the simultaneous equation system  is different  from  the single  equation  system  in  many  ways. The  most  prominent difference is that in  SEM the  independent variables can be both  lagged-endogenous and  exogenous whereas in the single  equation model independent variable is always exogenous. Secondly, an equation of SEM should not be solved independently without consider other equations. We  present  the main differences between single equation and the SEM in  Table below.