Third,Conclusion
To sum up,the faction of system functional linguistics ,represented by Halliday,is now one of most influent linguistics factions in the world .It has gained great achievements in several aspacts.But any theory has to continue improving and becoming perfect by absorbing "rich nutrition" from other theories as the development of itself.Any theory must absorb nutrition from others to gain greater advantage,so is it with the systemic functional linguistics itself which has also something immature and needs to draw lessons from other theories or subjects to supplement the inadequacy of itself.