Manual construction of ontologies for the SemanticWeb is a time consuming task. In order to help humans, the ontology learning field tries to automate the construction of new ontologies. The amount of data caused by the success of Internet is demanding methodologies and tools to automatically extract unknown and potentially useful knowledge out of it, generating structured representations with that knowledge. Although ontological engineering tools have matured over the last decade , manual ontology acquisition remains a tedious, time-consuming, error prone, and complex task that can easily result in a knowledge acquisition bottleneck. Besides, while the new necessities of information are growing, the available ontologies need to be updated, enriched with new contents. The research on the ontology learning field has made possible the development of several approaches that allow the partial automation of the ontology construction process. It aims at reducing the time and effort in the ontology development process. Some methods and tools have been proposed in the last years, to speed up the ontology building process, using different sources and several techniques. Computational linguistics techniques, information extraction, statistics, and machine learning are the most prominent paradigms applied until now. There are also a great variety of information sources used for ontology learning. Though Web pages, dictionaries, knowledge bases, semi-structured and structured sources can be used to learn an ontology, most of the methods only use textual sources for the learning process. All methods and tools have a strong relationships to the type of processing performed. In summary, the ontology learning field puts a number of research activities together, which focus on different types of knowledge and information sources, but share their target of a common domain conceptualisation The ontology learning is a complex multi-disciplinary field that uses the natural language processing, text and web data extraction, machine learning and ontology engineering. … Ontology Learning