Elnaz Rezaei Ehsan - Master's degree, industrial engineering, system management and productivity, Iran University ofScience and Technology
Kazem Taghandiki - Department of Computer Engineering, Technical and Vocational University, Tehran, Iran

Today, the web has become a mandatory platform to express users'opinions, emotions and feelings about various events. Every personusing his smartphone can give his opinion about the purchase of aproduct, the occurrence of an accident, the occurrence of a new disease,etc. in blogs and social networks such as (Twitter, WhatsApp, Telegramand Instagram) register. Therefore, millions of comments are recordeddaily and it creates a huge volume of unstructured text data that canextract useful knowledge from this type of data by using naturallanguage processing methods. Sentiment analysis is one of theimportant applications of natural language processing and machinelearning, which allows us to analyze the sentiments of comments andother textual information recorded by web users. Therefore, the analysisof sentiments, approaches and challenges in this field will be explainedin the following.

Sentiment analysis, natural language processing, opinion mining,machine learning, dataset