Within the broad field of Artificial Intelligence (AI), Machine Learning (ML) looks at improving the performances of computers in executing tasks for which they were not specifically pre-programmed. Applied to the field of Natural Language Processing (NLP), ML helps computers to autonomously learn tasks such as the recognition, understanding and generation of natural language (i.e. the lan- guage spoken by humans). In other words, ML applied to NLP refers to the ability of humans to interact with computers in the same way in which humans interact among themselves. On the part of the computers this implies being able to understand human language, to understand its meaning, and to interact with it thorough the generation of new language