I. Introduction
Sentiment analysis is widely used for analyzing opinions of people towards various entities such as products, services, topics etc. and there by evaluating customer satisfaction. It is also named as opinion mining which consists of large problem space. Sentiment analysis includes Natural Language Processing (NLP), text analysis and computational linguistics for identifying and extracting subjective information in source materials – for example, checking whether a review is positive or negative. Analysis of sentiments, extraction of opinion, mining sentiments and opinion, subjectivity analysis, emotion analysis, review mining etc. is different names used for slightly different tasks.