Due to increasingly use of various social-sites the Sentiment Analysis become a popular area for research. Various companies are using these social sites to check whether their customers are satisfied with the services provided by them or not. In this paper, different techniques for Sentiment Classification are described in detail. Also the various existing Hybrid techniques are studied. This paper also represents the research gaps of these techniques which are useful for the future work.

Keywords : Sentiment Analysis , Sentiment Classification Levels , Twitter , Hybrid , Machine Learning Techniques.