Nowadays, computers are capable of storing massive amounts of information interconnected in a large-scale network, the Internet. These characteristics make indispensable tools that can retrieve specific information from this network. One of these key applications is a question answering system. More precisely, query logs have shown that a particular type of question is very prominent: definition questions (e.g., "Who was Martin Luther?" and "What is a solar panel?"). Broadly speaking, the answer to this sort of query comprises an array of pieces of relevant information about the concept...