The Chatbots are the computer programs that interact with the users using natural language. The chatbot stores the information in the database to identify the keywords from the sentences and make a decision for the query and answers the question. In this paper keyword, ranking and sentence similarity calculation is done using n-gram, TF-IDF and cosine similarity. From the given input sentence, the score will be obtained for each sentence and more similar sentences are obtained for the given query. The query posed to the bot which isn't comprehended or not present in the database is further processed by the third party, expert system.