Natural language processing techniques are used in sentiment analysis algorithms to process and analyze text. NLP leverages multiple classification techniques such as:
Stemming. Reducing a word to its root form.
Tokenization. Breaking up a string of text into word units or tokens.
Part-of-speech tagging. Tagging tokens with a speech category such as verb, adjective, noun, etc.
Parsing. How words are connected and sentences are structured.
Lexicons. A list of words and expressions.